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Zdziennicka, Anna, Katarzyna Szymczyk, and Bronisław Jańczuk. "Wettability of Quartz by Ethanol, Rhamnolipid and Triton X-165 Aqueous Solutions with Regard to Its Surface Tension." Colloids and Interfaces 7, no. 4 (December 15, 2023): 71. http://dx.doi.org/10.3390/colloids7040071.
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The wettability of quartz by different liquids and solutions plays a very important role in practical applications. Hence, the wetting behaviour of ethanol (ET), rhamnolipid (RL) and Triton X-165 (TX165) aqueous solutions with regard to the quartz surface tension was investigated. The investigations were based on the contact angle measurements of water (W), formamide (F) and diiodomethane (D) as well as ET, RL and TX165 solutions on the quartz surface. The obtained results of the contact angle for W, F and D were used for the determination of quartz surface tension as well as its components and parameters using different approaches, whereas the results obtained for the aqueous solution of ET, RL and TX165 were considered with regard to their adsorption at the quartz–air, quartz–solution and solution–air interfaces as well as the solution interactions across the quartz–solution interface. The considerations of the relations between the contact angle and adsorption of solution components at different interfaces were based on the components and parameters of the quartz surface tension. They allow us to, among other things, establish the mechanism of the adsorption of individual components of the solution at the interfaces and standard Gibbs surface free energy of this adsorption.
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Boniello, G., A. Stocco, C. Blanc, and M. Nobili. "Comment on “Brownian diffusion of a particle at an air/liquid interface: elastic (not viscous) response of the surface”." Physical Chemistry Chemical Physics 19, no. 33 (2017): 22592–93. http://dx.doi.org/10.1039/c7cp02970e.
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In a recent article Toro-Mendoza et al. considered an elastic response of an interface in order to explain the enhanced lateral drag of solid particles straddling fluid interfaces we recently measured.
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Borrel, Pascale. "Gestes de surface : Touching Reality de Thomas Hirschhorn et What Shall We Do Next? de Julien Prévieux." Interfaces, no. 40 (December 21, 2018): 55–65. http://dx.doi.org/10.4000/interfaces.601.
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Favaro, Marco. "(Invited) In Situ Photoelectron Spectroscopy Reveals the Chemical Nature of Semiconductor Surface States." ECS Meeting Abstracts MA2023-02, no. 48 (December 22, 2023): 2434. http://dx.doi.org/10.1149/ma2023-02482434mtgabs.
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The accessible photovoltage of semiconducting photoabsorbers is typically 0.5-1 V below the theoretically achievable values predicted by the Shockley-Queisser limit [1]. Although the reason for this is still not well understood, surface and interface states within the photoabsorbers energy band gap may play a crucial role as they generally induce Fermi level pinning [2]. Within the PEC community, two key elements have been identified for the maximization of the photovoltage in photoelectrodes for water splitting: (i) the passivation of surface defects which is needed to avoid Fermi level pinning, and (ii) the increase of the minority carrier concentration at the interface to improve contact selectivity and optimize carrier extraction [3,4]. To understand the role of surface defects on Fermi level pinning, detailed information on the chemical nature and electronic properties of surface states is needed. Such information is usually obtained with UHV surface science techniques such as XPS, but the photoelectrode surface under UHV conditions has little, if any, relevance to the electrified surface when immersed in the electrolyte. Moreover, recent studies have shown that semiconductor surfaces are not static, but undergo extensive structural and chemical transformations during PEC device operation [5,6]. In this talk, we will show our recent development of state-of-the-art techniques to study the structure and dynamics of semiconductor/water interfaces under practically relevant conditions [7]. The chemical nature of the electronic states for selected semiconductors prepared at the Institute for Solar Fuels has been explored using synchrotron-based resonant, ambient pressure soft and hard X-ray photoelectron spectroscopy (AP-XPS and AP-HAXPES) [6,8-11], and with in situ/operando Raman and photoluminescence spectroscopy. In particular, we will show that it is possible to study photon-induced chemical changes at solid/liquid interfaces using AP-XPS and AP-HAXPES [6,8]. We will conclude this contribution by discussing about future perspectives and technical implementations for multimodal in situ/operando investigations of photoelectrocatalytic processes. [1] M.T. Mayer. Curr. Opin. Electrochem. 2017, 2, 104. [2] A. J. Bard et al. J. Am. Chem. Soc. 1980, 102, 3671. [3] A.G. Scheuermann et al., Nat. Mater. 2016, 15, 99. [4] M. Schleuning et al., Sustainable Energy Fuels, 2022, 6, 3701. [5] F.M. Toma et al., Nat. Commun. 2016, 7, 12012. [6] M. Favaro et al., J. Phys. Chem. B 2018, 122, 801. [7] M. Favaro et al., Surf. Sci. 2021, 713, 121903. [8] M. Favaro et al., J. Phys. D: Appl. Phys. 2021, 54, 164001. [9] M. Favaro et al., J. Phys. Chem. C 2019, 123, 8347. [10] W. Wang et al., J. Am. Chem. Soc. 2022, 144, 17173. [11] P. Schnell et al., Sol. RRL 2023, 2201104.
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Zdziennicka, Anna, Edyta Rekiel, Katarzyna Szymczyk, Wojciech Zdziennicki, and Bronisław Jańczuk. "Wetting Behaviour of Water, Ethanol, Rhamnolipid, and Triton X-165 Mixture in the Polymer–Solution Drop–Air System." Molecules 28, no. 15 (August 3, 2023): 5858. http://dx.doi.org/10.3390/molecules28155858.
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Despite the fact that the wetting properties of multicomponent mixtures including the surface active compounds play a very important role in many practical applications, they are not sufficiently known. Thus, the wettability of polytetrafluoroethylene (PTFE) and poly (methyl methacrylate) (PMMA) by the water + ethanol (ET) solution of rhamnolipid (RL) with Triton X-165 (TX165) mixture was studied. The investigations involved measuring the advancing contact angles of this solution on PTFE and PMMA by varying the concentration of TX165 while maintaining a constant concentration of ET and RL. Additionally, a thermodynamic analysis was conducted to obtain the compositions and concentrations of the ET, RL, and TX165 mixtures at the different interfaces. The composition and concentration of the interface mixed layer were considered using two different approaches to the wetting process. From these considerations, it follows that, depending on the ET concentration, it is possible to form the TX165 + RL layer at the solid–water + ET mixed solvent, as well as the water + ET–air interfaces, but not at the solid–water and water–air ones. This conclusion is in accordance with the Gibbs standard free energy of adsorption of particular components of the studied mixture at the solution–air and solid–solution interfaces.
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Howe, J. M. "Quantification of order in the liquid at a solid-liquid interface by high-resolution transmission electron microscopy (HRTEM)." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 114–15. http://dx.doi.org/10.1017/s0424820100163034.
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A number of different theoretical approaches have been used to model the atomic structure and properties of solid-liquid interfaces. Most calculations indicate that ordering occurs in the first several layers of the liquid, adjacent to the crystal surface. In contrast to the numerous theoretical investigations, there have been no direct experimental observations of the atomic structure of a solid-liquid interface for comparison. Saka et al. examined solid-liquid interfaces in In and In-Sb at lattice-fringe resolution in the TEM, but their data do not reveal information about the atomic structure of the liquid phase. The purpose of this study is to determine the atomic structure of a solid-liquid interface using a highly viscous supercooled liquid, i.e., a crystal-amorphous interface.
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Vivian, Robert. "Interfaces glace-roche et érosion sous-glaciaire." Revue de géographie alpine 76, no. 2 (1988): 207–18. http://dx.doi.org/10.3406/rga.1988.2707.
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Huynh, Kenny, Michael Evan Liao, Xingxu Yan, John Tomko, Thomas Pfeifer, Viorel Dragoi, Nasser Razek, et al. "Stability of Interface Morphology and Thermal Boundary Conductance of Direct Wafer Bonded GaN|Si Heterojunction Interfaces Annealed at Growth and Annealing Temperatures." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1605. http://dx.doi.org/10.1149/ma2023-02331605mtgabs.
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The properties of thin (~2 um) GaN templates on a silicon support substrate were studied to assess the stability of the direct wafer bonded GaN / Si interface. EVG® ComBond® equipment was used for bonding under high vacuum (~10-8 mtorr) at room temperature to remove unwanted native surface oxides [1,2]. For the bonded samples, the [1010] GaN edge was aligned parallel to the Si [110] edge. An X-ray diffraction reciprocal space map of the (004) Si and (0004) GaN revealed that there is a ~0.2° tilt between the GaN and Si layers and is simply due to the relative miscut between the two wafers. The treatment of the surfaces prior to bonding produces an amorphous region at the bonded interface that has been seen in many other bonded systems [3-5]. In the as-bonded sample, high resolution scanning transmission electron microscopy revealed a ~2 nm amorphous region on the Si side of the bonded interface, as confirmed by energy dispersive x-ray spectroscopy (EDX). Subsequent annealing was performed in an effort to recrystallize the amorphous interface. Previous work has shown that recrystallization between Si|Si wafer bonded samples occurred when annealed at 450 °C for 12 hours [3]. However, in the GaN|Si system, we found that the amorphous interface did not recrystallize when annealed under those conditions. Annealing at temperatures up to 450 °C and 120 hours showed only initial stages of interdiffusion and a stable interface. However, after annealing at 700 °C for 24 hours, high resolution EDX revealed the formation of amorphous SiN as well as the diffusion of gallium into silicon. Preliminary thermal results show that the thermal boundary conductance (TBC) of the as bonded sample is ~140 MW/(m2K). The TBC results of wafer bonded GaN|Si reported here is higher than previously reported TBC values of epitaxially grown interfaces such as GaN on Si [6], GaN on SiC [7], and GaN on diamond [8]. The TBC for the annealed interface is degraded by a factor of two compared to the as-bonded interface for the sample that was annealed at 700 °C for 24 hours. These results demonstrate that high TBC can be achieved through wafer bonding of GaN with materials such as silicon and that such interfaces are stable even up to device operation up to 300 °C. However, chemically rough interfaces formed due to high temperature annealing are detrimental to thermal transport across these interfaces. V. Dragoi, et al., ECS Trans., 86(5), 23 (2018) C. Flötgen, et al., ECS Trans., 64(5), 103 (2014) M.E. Liao, et al., ECS Trans., 86(5), 55 (2018) Y. Xu, et al., Ceramics International, 45, 6552 (2019) F. Mu, et al., Appl. Surf. Sci., 416, 1007 (2017) L. Yates, et al., ASME InterPACK (2015) J. Cho, et al., Phys. Rev. B, 89, 115301 (2014) H. Sun, et al., APL, 106(11), 111906 (2015) Figure 1
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Qu, Jianzhou, Zhou Yu, and Alexander Urban. "The Mechanism of Hydrogen Evolution Reaction at the Buried Interface of Silica-Coated Electrocatalysts." ECS Meeting Abstracts MA2023-01, no. 36 (August 28, 2023): 2104. http://dx.doi.org/10.1149/ma2023-01362104mtgabs.
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Semipermeable oxide coatings can protect electrocatalysts in harsh environments without reducing the catalytic performance (Labrador, Esposito et al. ACS Catal. 8, 2018, 1767–1778), making them attractive for direct seawater electrolysis. We recently showed that the buried SiO2/Pt interface of silica-coated platinum electrocatalysts is environment-dependent and changes with the pH value of the electrolyte and the electrode potential (Qu and Urban, ACS Appl. Mater. Interfaces 12, 2020, 52125–52135). Here, we discuss the impact of silica membrane coatings on the hydrogen evolution reaction (HER) mechanism at the interface with different transition-metal surfaces. Stable configurations of the buried SiO2/TM interface at HER conditions were determined using density-functional theory (DFT) calculations. Computed Pourbaix diagrams for different transition-metal substrates show the pH and potential dependence of reaction intermediates and the hydrogen coverage on the metal surface. Our results indicate that the HER mechanism at the buried SiO2/catalyst interfaces may involve the silica membrane. Hence, besides the protective quality of silica membranes, this also points to the possibility of designing synergistic membrane-coated electrocatalysts that surpass the bare surfaces of earth-abundant transition metals in terms of catalytic performance (stability, activity, and/or selectivity).
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Degoulange, Damien, Raj Pandya, Michael Deschamps, Dhyllan A. Skiba, Betar M. Gallant, Sylvain Gigan, Hilton B. de Aguiar, and Alexis Grimaud. "Micrometer Thick Interfaces in Aqueous Biphasic Systems for Electrochemical Devices." ECS Meeting Abstracts MA2023-01, no. 1 (August 28, 2023): 460. http://dx.doi.org/10.1149/ma2023-011460mtgabs.
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Aqueous biphasic systems (ABSs) consist of two immiscible phases composed of only one solvent (water) with the phase separation driven by solutes such as polymers, ionic liquids and salts. Such two-phase systems have proved highly relevant in recent years for applications in electrochemical devices. Indeed, highly concentrated solutions of LiTFSI, so called “Water-in-salt” battery electrolyte, were recently found to form an ABS with LiX (with X=Cl, Br, I) aqueous solutions (Dubouis et al., ACS Cent. Sci. 2019, 5, 640-643 and Dubouis et al., J. Phys. Chem. B 2021, 125, 5365-5372). These LiTFSI-LiX ABSs enable the intercalation at high potential of halides such as Cl- or Br- into graphite, in lieu of the oxidation of water or the evolution of halogenated gas, thus enabling the assembly of efficient dual-ion batteries (Yang et al., Nature 2019, 569, 245-250). Similarly, ABS have been proposed to prevent problematic crosstalk mechanisms as observed in Li-ion/sulfur batteries (Yang et al., Proc. Natl. Acad. Sci. 2017, 114, 6197-6202) or to be used to design membraneless redox flow batteries (Navalpotro et al., Adv. Sci. 2018, 5, 1800576). However for ABS to be widely implemented in electrochemical devices, the ion transfer at liquid/liquid interface is key in obtaining good (dis)charge rate and preventing self-discharge. Thus, it is crucial to first understand the structure and chemistry of these aqueous interfaces. We studied the LiTFSI-LiCl ABS first with Fourier transform infrared spectroscopy (FT-IR) and surface tension measurement to assess ion partition and surface tension respectively. Both ion partition and surface tension are found increasing as function of increasing concentration. Such trend of the surface tension is typical of a negative adsorption of ions at the liquid/liquid interface. Using high spatial resolution Raman imaging, we were able to confirm a negative adsorption of ions by assessing the ion concentration profiles at the interface between the two aqueous phases. Indeed, we found concentration profiles of water and ions to be sigmoidal which is characteristic of a negative adsorption. Strikingly, the length of the negative adsorption is ranging from 11 to 2 μm with increasing concentrations and the Raman spectra of water and TFSI anion are continuously changing along the interface from an environment with weak hydrogen bounding network and with anion aggregate to an environment similar to diluted solutions. Moreover, when changing the cation from Li+ to H+, the temperature dependence of the phase diagram is inversed, as we could show by variable temperature nuclear magnetic resonance (VT-NMR) and micro-calorimetry, but the interface is still few microns thick. Thus, we revealed a continuous change in the chemical environment between two aqueous phases at the micrometer scale, which contrast drastically with the interface between two immiscible electrolyte solutions (ITIES) such as oil-water systems where molecularly sharp, nanometer interface are found. Such difference raise question about the impact of the thickness and the chemical composition of the interface on the dynamics of ion and electron transfer at the interface, that we are studying by electrochemical measurements. Furthermore, this work paves the way to compare liquid/liquid and solid/liquid interfaces in order to understand how ion solvation affects the interfacial ion transfer and thus enable a better engineering of the electrolyte and ABSs for better electrochemical devices.
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Magnussen, Olaf M. "Operando Studies of Electrochemical Interfaces By High-Energy Surface x-Ray Scattering." ECS Meeting Abstracts MA2023-02, no. 55 (December 22, 2023): 2679. http://dx.doi.org/10.1149/ma2023-02552679mtgabs.
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Knowledge on the atomic-scale structure of the electrode-electrolyte interface is of key importance for understanding electrochemical reactivity. This includes the structure of the atomic layers at the electrode surface, the arrangement of chemisorbed species on the surface, and the near-surface structure of the adjacent electrolyte, i.e., the electrochemical double layer. Surface X-ray scattering (SXRD) methods can provide such information and have been used for decades to obtain important insights into various structural aspects of electrochemical systems. However, conventional SXRD is limited by the considerable time required for a full characterization of the three-dimensional interface as well as in terms of the structural detail that can be reliably extracted from the diffraction data by structural models. This is related to the slow sequential data acquisition necessary for such measurements. We here describe in situ and operando studies of electrochemical interface structure by High Energy Surface X-ray Diffraction (HESXRD), where the interface structure is probed by hard X-rays with high photon energy (in this work 70 keV). This method has been originally developed for studies of catalyst surfaces in the gas phase [1], but is starting to be applied increasingly to electrochemical systems. In combination with the highly brilliant beams provided by emerging hard X-ray 4th generation synchrotron, HESXRD allows to obtain very large datasets in short time. From these the interface structure can be determined with unprecedented detail by a quantitative analysis of the measured crystal truncation rods (CTRs). Furthermore, measurement of restricted datasets is possible with even high time resolution down to the second or sub-second regime, which is ideal for monitoring fast kinetic changes in operando. We illustrate the capabilities of HESXRD by studies of platinum surface oxidation and magnetite single crystal electrodes under oxygen evolution conditions. For the case of platinum we present data on Pt(111), Pt(100), and Pt(110) in 0.1 M HClO4 that reveal distinct differences in the structure and formation mechanisms of the Pt surface oxide [2]. Because of these differences, the irreversible surface restructuring and Pt dissolution during oxidation/reduction cycles depends strongly on the crystallographic orientation. In addition, we demonstrate for Pt(111) that the extraction of Pt atoms out of the electrode surface in the initial stages of oxidation is not directly coupled to the charge transfer associated with the formation of adsorbed oxygen species [3]. Studies on magnetite focus on Fe3O4(100) in 0.1 M NaOH, where previous SXRD studies showed that the (√2x√2)R45° reconstructed surface formed under UHV conditions can be maintained [4]. HESXRD allowed to obtain extended CTR datasets, which provide deeper insights into the structure of this oxide model electrocatalyst. [1] J. Gustafson et al., Science 343, 758 (2014) [2] T. Fuchs et al., Nature Catalysis 3, 754 (2020) [3] T. Fuchs et al., J. Phys. Chem. Lett. 14, 3589 (2023), https://doi.org/10.1021/acs.jpclett.3c00520 [4] D. Grumelli et al., Ang. Chem. Int. Ed. 59, 49 (2020)
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Hafidi, K., M. Azizan, Y. Ijdiyaou, and E. L. Ameziane. "Ètude des interfaces SiO2/TiO2 et TiO2/SiO2 dans la structure SiO2/TiO2/SiO2/c-Si préparée par pulvérisation cathodique radio fréquence." Canadian Journal of Physics 85, no. 7 (July 1, 2007): 763–76. http://dx.doi.org/10.1139/p07-053.
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The atomic structure of the TiO2/SiO2 and SiO2/TiO2 interfaces has been investigated in SiO2/TiO2/SiO2 multilayers deposited by radio frequency reactive sputtering without breaking the vacuum on the crystalline substrate cooled by water. The characterizations of these interfaces have been performed using three complementary techniques sensitive to surface and interface state: X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXD), and specular X-ray reflectometry (GIXR). The concentration profiles and Si2p and O1s core level chemical displacements show that TiO2/SiO2 and SiO2/TiO2 interfaces are very diffuse. The reflectometry measurements confirm this character and indicate that the silicon, titanium, and oxygen atomic concentrations vary gradually at the interfaces. The grazing incidence X-ray spectra indicates that the interfacial layers are not well crystallized and are formed by SiO2-TiO2, TiO, Ti2O3, Ti3O5, Ti5Si3, Ti5Si4, TiSi, and TiSi2 components.
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Grunder, Yvonne. "Perspectives and Impact of in-Situ X-Ray Techniques for Electrodeposition." ECS Meeting Abstracts MA2022-02, no. 24 (October 9, 2022): 1003. http://dx.doi.org/10.1149/ma2022-02241003mtgabs.
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In-situ surface x-ray diffraction has enabled an atomic/molecular-level understanding of the electrochemical interface, including its potential and time dependence, to be developed. [1] Specifically, for electrodeposition the influence of additives and adsorbates onto growth and nucleation behaviour could be established. Halogens on metal surfaces are prototypic adsorbate systems but the adsorption of halide ions especially on copper is also of major importance for on-chip metallization in ULSI microchip production. Halide ions on Cu surfaces form an inhibiting adsorbate layer with polyethylene glycol (PEG). Even though the influence of the additives combination on the shape evolution of the Cu deposit was subject of numerous studies, their precise role during the elementary steps of the deposition with regards to altering the charge distribution and dipole moment at the interface is largely not understood. [1] While information about the atomic structure of the electrode surface in electrochemical in-situ cells has been widely investigated, insight into the charge distribution and the structure of the electrolyte at the interface is still lacking. Combining x-ray spectroscopy and x-ray diffraction to gain site-specific information about the charge distribution at buried interfaces is a promising tool. [2,3,4] Studies on the metal-halide interface and how the use of surface x-ray scattering techniques can help to characterise electrochemical interfaces in-situ in order to link, structure and stability and morphology changes will be presented. [1, 4] Advances in these directions offer possibilities in elucidating atomic scale models of the electrochemical interface and thus will help to establish structure-stability-reactivity relationships which will help to understand growth kinetics and nucleation behaviour. References: [1] In-Situ Surface X-ray Diffraction Studies of Copper Electrodes: Atomic-Scale Interface Structure and Growth Behavior. Gruender, Y., Stettner, J., & Magnussen, O. M. (2018). Journal of the Electrochemical Society; 166(1), D3049-D3057. doi:10.1149/2.0071901jes [2] Probing the charge distribution at the electrochemical interface; Y. Gründer and C. A. Lucas, Physical Chemistry Chemical Physics, 2017, 19, 8416 [3] Simulation of Surface Resonant X-ray Diffraction; Y. Joly et al., J. Chem. Theory Comput,. 2018, 14, 973−980 [4] Charge Reorganization at the Adsorbate Covered Electrode Surface Probed through in Situ Resonant X-ray Diffraction Combined with ab Initio Modeling;Y. Grunder, C. A. Lucas, P. B. J. Thompson, Y. Joly, Y. Soldo-OlivierJ. Phys. Chem. C 2022, 126, 9, 4612–4619
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Deka, Nipon, and Rik Mom. "Probing of Near-Surface Cations during the Oxygen Evolution Reaction (OER) Using Operando XAS." ECS Meeting Abstracts MA2023-02, no. 55 (December 22, 2023): 2669. http://dx.doi.org/10.1149/ma2023-02552669mtgabs.
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Electrified solid-liquid interfaces are ubiquitous in technologies ranging from colloidal science to electrochemistry. Hence, an atomic-level characterization of the electrode-electrolyte interface is crucial for total control and optimization of the processes involved. While the electrode side of the interface has been quite extensively studied, the electrolyte side is comparatively poorly understood1. Specifically probing the near-surface electrolyte species during an electrochemical reaction is a major technical challenge in the field of catalysis and surface chemistry. We have developed an interface-sensitive X-ray absorption spectroscopy (XAS) approach which allows us to directly probe the near-surface cations and anions of the electrolyte under applied potentials. In this approach, we employ a mesoporous electrocatalyst film coated on a 𝑆𝑖𝑁𝑥 X-ray window. These mesoporous films exhibit an extremely high electrode-electrolyte interface area, enabling us to specifically probe the behaviour of interfacial ions via their K-edge spectra. Using this approach, we have recently investigated the interaction of Na+ cations with IrOx during the oxygen evolution reaction (OER), which is a bottleneck in major electrochemical processes like green hydrogen production and CO2 reduction. The cations and anions of the electrolyte reportedly influence the OER activity of electrodes during OER2,3. We used operando Na K-edge XAS to directly probe the concentration and coordination environment of the near-surface Na+ cations. Simultaneously, operando O K-edge XAS monitored the interfacial water structure and the evolution of catalyst’s surface structure. Contrary to expectations, we discovered that the positively charged Na+ ions are drawn to the IrOx surface by more positive potentials only at alkaline pH. This finding cannot be explained by any of the electrolyte theories4 put up thus far, emphasizing the necessity of a detailed investigation of interfacial electrolyte structures. References: Arminio-Ravelo et al. ChemPhysChem 20, (2019). Tymoczko et al. Catal. Today 244, (2015). Ganassin et al. Phys. Chem. Chem. Phys. 17, (2015). Waegele et al. J. Chem. Phys. 151, (2019). Figure 1
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Chau, Allison L., Jonah Rosas, George D. Degen, Lisa K. Månsson, Jonathan Chen, Eric Valois, and Angela A. Pitenis. "Correction: Aqueous surface gels as low friction interfaces to mitigate implant-associated inflammation." Journal of Materials Chemistry B 8, no. 42 (2020): 9813. http://dx.doi.org/10.1039/d0tb90177f.
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Baeumer, Christoph. "(Invited) Electrochemistry Happens at the Interface." ECS Meeting Abstracts MA2023-02, no. 67 (December 22, 2023): 3208. http://dx.doi.org/10.1149/ma2023-02673208mtgabs.
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Earth-abundant, active, selective and stable electrocatalysts are the cornerstone in our transition to defossilisation of the chemical industry, sector coupling, and sustainable energy. The catalyst surface is known to transform at the interface to the electrolyte, especially under operation conditions. Only the properties of the transformed interface coupled to the underlying layer gives rise to observed metrics like activity and stability. This complicates predictive electrocatalyst materials design – a challenge which can only be tackled by collaborative and interdisciplinary efforts, at the Interface between Chemistry, Physics, Materials Science, and Engineering. I believe this presents one of the main tasks for the young electrochemistry researchers in Europe and around the world, especially since the same challenges also arise in related technologies like Li-ion batteries. In my talk I will discuss how the old wisdom from semiconductor research “the Interface is the device” can be translated into the current challenge “Electrochemistry happens at the Interface”. We need new approaches in designing and studying these electrochemical interfaces for fundamental insights that may in a next step yield better performance in future applications. The talk will be split in two parts. Firstly, I will introduce how single crystalline surfaces can be obtained using epitaxial thin films, and discuss how these can be used to derive atomic-level structure-property relations by synergetic experimental and theoretical investigation. Such films can be fabricated with unit-cell or even atomic-layer precision and enable direct comparison to single facets typically investigated in density functional theory. Secondly, I will discuss opportunities and challenges in surface-sensitive operando characterization in a liquid medium.1 Information from the outermost surface of a catalyst can be obtained through a standing-wave approach2,3 or extraction of a surface-only signal from careful thickness-dependent studies.4 In my ERC project “Interfaces at work”, we are also developing interface-sensitive, laboratory-based operando X-ray photoelectron spectroscopy approaches based on the new XPS user facility at the University of Twente. Throughout the talk, I will refer to examples from LaNiO3 thin films, which are atomically flat both before and after application as electrocatalysts for the OER during water electrolysis. We selectively tuned the surface cationic composition in epitaxial growth. The Ni-termination is approximately twice as active for the OER as the La-termination.2 Our ex situ and operando characterization confirmed that the surface transformation pathways – and therefore the electrochemical functionality – depend on a single atomic layer at the surface. A second example will be the introduction of multi-cation compositions in so-called high entropy perovskite oxides (HEO), which can maximize the catalytic activity. The HEO LaCr0.2Mn0.2Fe0.2Co0.2Ni0.2O3-δ outperforms all of its parent compounds (single TM-site element in the LaTMO3 perovskite) by orders of magnitude.5 X-ray photoemission studies reveal a synergistic effect of simultaneous oxidation and reduction of different transition metal cations during adsorption of reaction intermediates. Rao, R. R., van den Bosch, I. C. G. & Baeumer, C. Operando X-ray characterization of interfacial charge transfer and structural rearrangements. in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering 1–24 (Elsevier, 2023). doi:10.1016/B978-0-323-85669-0.00068-4. Baeumer, C. et al. Tuning electrochemically driven surface transformation in atomically flat LaNiO3 thin films for enhanced water electrolysis. Nat Mater 20, 674–682 (2021). Martins, H. P. et al. Near total reflection x-ray photoelectron spectroscopy: quantifying chemistry at solid/liquid and solid/solid interfaces. J Phys D Appl Phys 54, 464002 (2021). Baeumer, C. Operando characterization of interfacial charge transfer processes. J Appl Phys 129, 170901 (2021). Kante, M. V et al. A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation. ACS Nano (2023) doi:10.1021/acsnano.2c08096. Figure 1
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Pimponi, D., M. Chinappi, P. Gualtieri, and C. M. Casciola. "Hydrodynamics of flagellated microswimmers near free-slip interfaces." Journal of Fluid Mechanics 789 (January 22, 2016): 514–33. http://dx.doi.org/10.1017/jfm.2015.738.
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The hydrodynamics of a flagellated micro-organism is investigated when swimming close to a planar free-slip surface by means of numerical solutions of the Stokes equations obtained via a boundary element method. Depending on the initial conditions, the swimmer can either escape from the free-slip surface or collide with the boundary. Interestingly, the micro-organism does not exhibit a stable orbit. Independently of escape or attraction to the interface, close to a free-slip surface, the swimmer follows a counter-clockwise trajectory, in agreement with experimental findings (Di Leonardo et al., Phys. Rev. Lett., vol. 106 (3), 2011, 038101). The hydrodynamics is indeed modified by the free surface. In fact, when the same swimmer moves close to a no-slip wall, a set of initial conditions exists which result in stable orbits. Moreover, when moving close to a free-slip or a no-slip boundary, the swimmer assumes a different orientation with respect to its trajectory. Taken together, these results contribute to shed light on the hydrodynamical behaviour of micro-organisms close to liquid–air interfaces which are relevant for the formation of interfacial biofilms of aerobic bacteria.
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Listorti, Andrea, Sara Covella, Alberto Perrotta, Francesca Russo, Fabio Palumbo, Antonella Milella, Vincenza Armenise, Francesco Fracassi, Aurora Rizzo, and Silvia Colella. "(Invited) Plasma Processes on Metal Halide Perovskite Interfaces for Photovoltaic Applications." ECS Meeting Abstracts MA2023-01, no. 14 (August 28, 2023): 1342. http://dx.doi.org/10.1149/ma2023-01141342mtgabs.
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Metal Halide Perovskite (MHP) semiconductors are currently standing out for their exceptional optoelectronic properties and, particularly, for their exploitation in photovoltaics. Their structure can be described by the formula , where A is usually an organic cation, such as methylammonium (MA) or formamidinium (FA), B is a metal cation and X is a halogen anion, typically I or Br. The exceptional properties of MHPs derive by their hybrid organic-inorganic nature, which also allows for low-cost fabrication processing. The raise of perovskite photovoltaics 1 followed progresses on three main research fronts: i) material deposition optimization, ii) material compositional tuning and iii) device interface engineering. The interfaces play a fundamental role in the device function affecting charge extraction, recombination processes and material/device overall stability. Therefore, to further improve the performances of these devices, many surface processes have been applied to solar cells interfaces, most of which include a solution-based methodology 2. The aim of these treatments is not only to improve solar cells efficiency in terms of carrier concentration and transport properties, but also to improve the device stability under working conditions, which is one of the main issues of these materials. Among the different surface treatments exploitable, the use of plasma represents a solvent-free and non-invasive promising strategy to boost MHP solar cells performances. Plasma-deposited coatings on perovskite, as fluorocarbon polymers, have shown to improve material resistance to humidity and photoluminescence properties 3. We have explored the effect of low-pressure plasmas fed with different gases, namely Ar, , and , on Metylammonium Lead Iodide surface4. An interesting improvement of perovskite photoluminescence and solar cell efficiency was observed for Ar and plasma treatments, ascribable both to the removal of organic components, proven to be beneficial to device performances 5, and to other chemical and morphological modifications depending on the gas used. Starting from these results, new plasma surface treatments, plasma-assisted deposition and encapsulation processes will be object of study of future research, to achieve a more complete understanding of the interfacial defects and charge carrier dynamics and to further minimize performance losses and instability issues. References NREL Best Research-Cell Efficiency Chart. https://www.nrel.gov/pv/cell-efficiency.html Han TH, Tan S, Xue J, Meng L, Lee JW, Yang Y. Interface and Defect Engineering for Metal Halide Perovskite Optoelectronic Devices. Advanced Materials. 2019;31(47). doi:10.1002/adma.201803515 Armenise V, Colella S, Milella A, Palumbo F, Fracassi F, Listorti A. Plasma-Deposited Fluorocarbon Coatings on Methylammonium Lead Iodide Perovskite Films. Energies (Basel). 2022;15(13):4512. doi:10.3390/en15134512 Andrea Listorti, Sara Covella, Alberto Perrotta, et al. A study on plasma-assisted modifications of Methylammonium Lead Iodide Perovskite surfaces for photovoltaic applications. Xiao X, Bao C, Fang Y, et al. Argon Plasma Treatment to Tune Perovskite Surface Composition for High Efficiency Solar Cells and Fast Photodetectors. Advanced Materials. 2018;30(9):1-7. doi:10.1002/adma.201705176 Figure 1
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Temperton, Robert, Mattia Scardamaglia, Suyun Zhu, and Andrey Shavorskiy. "Soft X-Ray Operando Characterization of Electrochemical Interfaces." ECS Meeting Abstracts MA2023-02, no. 55 (December 22, 2023): 2667. http://dx.doi.org/10.1149/ma2023-02552667mtgabs.
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HIPPIE is a high-flux, high-resolution soft x-ray beamline at MAX IV Laboratory (Sweden) with a new dedicated experimental setup for operando studies of electrochemical interfaces.[1] Such experiments utilize the dip-and-pull method to form a thin liquid meniscus on the surface of the working electrode in a three-electrode cell with a liquid electrolyte solution. Both the liquid film itself and the electrode-electrolyte interface can then be probed using X-ray photoelectron spectroscopy (PES) whilst maintaining full electrochemical control. The technique can be used to probe oxidation state changes, chemical shifts, electronic structure and electrochemical potentials in-situ. In this talk we will discuss status of spectroelectrochemical PES using soft X-rays, discussing the merits of the various different approaches to cell design. We will present three case studies on the topics of molecular redox reactions, battery interfaces and metal corrosion, all of which can be studied using dip-and-pull.[2-4] We will primarily aim to provide an introduction to the dip-and-pull method for those interested in this genre of advanced operando characterization. We will additionally outline the experimental realities and challenges that any potential new user of the dip-and-pull method should be aware of before applying for beamtime to conduct an experiment. The three case studies were all measured at HIPPIE, where the beamline operates in the 250-2000 eV range, providing access to the L absorption edges of many transition metals and the K edges of light elements. The dip-and-pull PES experiments are realized with an ambient-pressure hemispherical electron analyzer allowing measurements in vapor pressures up to 25 mbar. Electrochemical cells can therefore use aqueous electrolyte solutions as well as some organic solvents, including many of those common in batteries. An argon/nitrogen atmosphere glove box can be attached to the measurement chamber such that air sensitive materials can be studied. Typically foils or thin films are used for the working electrode. This apparatus therefore provides one of the most flexible platforms for electrochemical studies using soft-X-ray spectroscopy. References: [1] S. Zhu et al., HIPPIE: a new platform for ambient-pressure X-ray photoelectron spectroscopy at the MAX IV Laboratory, Journal of synchrotron radiation, 28, 624-636 (2021) [2] R. Temperton et al. “Dip-and-Pull Ambient Pressure Photoelectron Spectroscopy as a Spectroelectrochemistry Tool for Probing Molecular Redox Processes.” Journal of Chemical Physics 157 (24): 244701 (2022) [3] I. Källquist et al. “Potentials in Li-Ion Batteries Probed by Operando Ambient Pressure Photoelectron Spectroscopy.” ACS Applied Materials and Interfaces 14 (5): 6465–75 (2022) [4] A. Larsson et al. “In Situ Quantitative Analysis of Electrochemical Oxide Film Development on Metal Surfaces Using Ambient Pressure X-Ray Photoelectron Spectroscopy: Industrial Alloys.” Applied Surface Science 611: 155714 (2023) Figure 1
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Dravid, Vinayak P. "Bicrystallography and electron diffraction." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 702–3. http://dx.doi.org/10.1017/s0424820100149349.
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Traditionally grain (or phase) boundaries have been modelled using coincidence site lattice (CLS)-type geometrical treatments. However, CSL utilizes only the latticetranslational symmetry of the crystals and is not applicable to nonsymmorphic crystals or in cases where the point group symmetry elements are important. Pond and coworkers, in an elegant series of papers proposed a complete geometric description of bicrystal containing an interface, i.e. bicrystallography. The use and application of bicrystallography has important implications for interface/surface structure, thin film growth and small particle studies.Theoretical development of bicrystallography (or tricrystallography..etc.) is rather complete. However, same is not the case for experimental bicrystallography. There two important methods for bicrystal diffraction experiments: one is the plan-view technique, while the other involves edge-on interface parallel to the electron beam. Plan-view CBED can determine loss of symmetry due to RBT as demonstrated by Eaglesham et al. Dravid et al. used plan-view CBED to probe the symmetry of NiO-ZrO2(CaO) eutectic interfaces.
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Sartori, Andrea, Olaf M. Magnussen, and Bridget Murphy. "Role of Chemisorbing Species in Growth at Liquid Metal-Electrolyte Interfaces Revealed by in Situ X-Ray Scattering." ECS Meeting Abstracts MA2023-02, no. 55 (December 22, 2023): 2666. http://dx.doi.org/10.1149/ma2023-02552666mtgabs.
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Liquid-liquid interfaces offer intriguing possibilities for nanomaterials growth. Especially, growth at liquid metal surfaces has recently received renewed interest. Here, fundamental interface-related mechanisms that control the growth behavior in these systems are studied for the case of Pb halide compound formation at the interface between liquid mercury electrode and aqueous salt solutions, using in situ X-ray reflectivity and grazing incidence X-ray diffraction, supplemented by electrochemical measurements and optical microscopy. The nucleation and growth of these compounds at potentials in the regime of Pb de-amalgamation was investigated in NaX + PbX2 (X = F, Cl, Br) to systematically explore the role of the halide species. X-ray reflectivity studies reveal the rapid formation of well-defined ultrathin precursor adlayers in Cl- and Br-containing solution. This adlayer formation is followed by subsequent quasi-epitaxial growth of Pb(OH)X bulk crystals, that are oriented with the c-axis along the surface normal. In contrast, growth in F-containing solution proceeds by slow formation of a more disordered deposit, resulting in random bulk crystal orientations on the Hg surface. A detailed structural analysis of the Pb(OH)Br and Pb(OH)Cl precursor adlayers reveals that they determine the orientation of the subsequently formed bulk crystals, with the arrangement in the adlayer providing a template. Together with our previous results on the pseudo-epitaxial growth of PbFBr on Hg (A. Elsen, et al., Proc.Nat.Acad.Sci., 2013, 110, 6663), these data reveal the decisive role of the interface chemistry, especially the strong chemisorption of the anions bromide and chloride, in steering the formation of these textured deposits at the liquid metal surface.
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Wang, Xuehang. "(Invited) Revealing Charge Storage Processes at the Interfaces of Supercapacitor Electrodes." ECS Meeting Abstracts MA2023-02, no. 5 (December 22, 2023): 861. http://dx.doi.org/10.1149/ma2023-025861mtgabs.
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The fast development of electrochemical energy storage devices has revolutionized almost every aspect of modern life by enabling portable electronic devices, electric vehicles, and grid storage of renewable energy. To satisfy the growing industrial and consumer needs for energy storage systems with high output power and short recharge time, the electrode materials should have excellent high-rate performance.1 Electrical double-layer (EDL) capacitors exhibit high-rate capability and long-cycling life as they store charges electrostatically. Using ionic liquid (IL) as the electrolyte leads to a large voltage window but low capacitance. In this first session of the presentation, I will introduce a mathematical model to simulate the IL ion packing structure in nanopores. This model is capable of estimating the EDLC capacitance based on pore size distribution. Then, we further revealed that mixture IL ions can be selectively driven into the pores of different confinement levels, which was confirmed by solid-state NMR, and further explained by DFT simulation2. In the second part of the presentation, I will shift to pseudocapacitors, which are expected to have a much higher charge storage capacity than EDL capacitors and a much higher rate than batteries as they store energy through fast surface redox reactions.3 The emerging 2D material family, 2D transition metal carbides/nitrides MXenes, shows outstanding pseudocapacitive performance due to their ionophilicity, metallic conductivity, and highly reactive surfaces. The proper coupling between electrolyte and electrode is critical to increase energy and power density. In the organic electrolyte, we found that the solvent has a strong impact on the ion/solvent arrangement in 2D MXene material and hence the charge storage capability.4 In the aqueous electrolytes, we successfully introduced surface redox reactions to MXene electrodes by using the water-in-salt electrolytes and by adjusting the initial valence of Ti in Ti3C2 MXenes, which dramatically increases the capacitance of MXene in the neutral aqueous electrolytes5. References Simon, P.; Gogotsi, Y., Nat. Mater. 2020, 19 (11), 1151-1163. Wang, X.; Mehandzhiyski, A. Y.; et al., J. Am. Chem. Soc. 2017, 139 (51), 18681-18687. Fleischmann, S.; Mitchell, J. B.; et al., Chem. Rev. 2020, 120 (14), 6738-6782. Wang, X.; Mathis, T. S.; et al., Nat. Energy 2019, 4 (3), 241-248. Wang, X.; Mathis, T. S.; et al., ACS Nano 2021, 15 (9), 15274-15284.
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Yanina, Svetlana V., Matthew T. Johnson, Zhigang Mao, and C. Barry Carter. "On Devitrification of Monticellite (CaMgSiO4) Films Grown on (001)-Oriented Single-Crystal MgO." Microscopy and Microanalysis 4, S2 (July 1998): 590–91. http://dx.doi.org/10.1017/s1431927600023072.
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Silicate glasses are the most common constituents of intergranular phases which can be found in liquid-phase sintered ceramics [1]. Silicates are known to influence the structure of ceramic interfaces which, in turn, frequently affect mechanical properties of ceramic materials [2]. In earlier studies of silicate glasses on single-crystal alumina Ramamurthy et al [3] and Mallamaci [4] showed that the morphology of dewetted glass films and the mechanism of devitrification depend on the crystallographic orientation of the substrate surface. In continuation of these studies, results are presented on the dewetting behavior of monticellite (CaMgSi04) in contact with the (OOl)-oriented surface of single-crystal MgO. Due to the simplicity of sample preparation and availability of 3- dimensional topographic information, Atomic Force Microscopy (AFM) was used for surface characterization. These AFM results are complemented by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) data on the chemical composition and the structure of the glass-substrate interface.
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Huynh, Kenny, Michael Evan Liao, Thomas Pfeifer, Xingxu Yan, Bernhard Rebhan, Christoph Floetgen, Xiaoqing Pan, Patrick E. Hopkins, and Mark S. Goorsky. "Improved Thermal Boundary Conductance in Annealed Direct Wafer Bonded Si-Ge." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1606. http://dx.doi.org/10.1149/ma2023-02331606mtgabs.
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The evolution of structural and thermal properties of wafer bonded Si|Ge with annealing is investigated in this study. Theoretical work suggests that the thermal boundary conductance between amorphous Si and Ge provide improved thermal properties as compared to a crystalline Si to Ge interface, and wafer bonded systems provides a fabrication method to experimentally test this theory [1]. EVG® ComBond® equipment was used for bonding under high vacuum (~10-8 mtorr) at room temperature to remove unwanted native surface oxides [2-4]. The bombardment of the surfaces prior to bonding produces an amorphous region at the bonded interface that has been seen in many other bonded systems [5,6]. In the as-bonded sample, high resolution scanning transmission electron microscopy revealed a ~1.2 nm amorphous region at the bonded interface. Subsequent annealing was done in an effort to recrystallize the amorphous interface. Previous work has shown that recrystallization between Si|Si wafer bonded samples occurred when annealed at 450 °C for 12 hours [3]. After annealing at 600 °C for 2 hours, the amorphous interface was observed to decrease to ~0.9 nm. Complete recrystallization is observed when the sample was annealed at 600 °C for 48 hours. Preliminary thermal results show that the thermal boundary conductance (TBC) of the as bonded sample is 47 ± 5 MW/(m2K). The TBC for the sample annealed at 600 °C for 48 hours is 94 ± 5 MW/(m2K), an improvement by a factor of two compared to the as-bonded interface. These results demonstrate that the TBC can be improved through annealing of the interface and that improvements due to an amorphous-amorphous interface do not dominate the thermal boundary conductance in this system. We consider that the improvements are due to recrystallization of the interface and/or to increased interdiffusion, which has been observed to increase TBC in epitaxially grown Si-Ge interfaces [7]. K. Gordiz, et al., J. Appl. Phys., 121(2), p.025102 (2017) V. Dragoi, et al., ECS Trans., 86(5), 23 (2018) C. Flötgen, et al., ECS Trans., 64(5), 103 (2014) M.E. Liao, et al., ECS Trans., 86(5), 55 (2018) Y. Xu, et al., Ceramics International, 45, 6552 (2019) F. Mu, et al., Appl. Surf. Sci., 416, 1007 (2017) Z. Cheng, et al., Nature communications, 12(1), p.6901 (2021) Figure 1
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BANNER, MICHAEL L., and WILLIAM L. PEIRSON. "Tangential stress beneath wind-driven air–water interfaces." Journal of Fluid Mechanics 364 (June 10, 1998): 115–45. http://dx.doi.org/10.1017/s0022112098001128.
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The detailed structure of the aqueous surface sublayer flow immediately adjacent to the wind-driven air–water interface is investigated in a laboratory wind-wave flume using particle image velocimetry (PIV) techniques. The goal is to investigate quantitatively the character of the flow in this crucial, very thin region which is often disrupted by microscale breaking events. In this study, we also examine critically the conclusions of Okuda, Kawai & Toba (1977), who argued that for very short, strongly forced wind-wave conditions, shear stress is the dominant mechanism for transmitting the atmospheric wind stress into the water motion – waves and surface drift currents. In strong contrast, other authors have more recently observed very substantial normal stress contributions on the air side. The availability of PIV and associated image technology now permits a timely re-examination of the results of Okuda et al., which have been influential in shaping present perceptions of the physics of this dynamically important region. The PIV technique used in the present study overcomes many of the inherent shortcomings of the hydrogen bubble measurements, and allows reliable determination of the fluid velocity and shear within 200 μm of the instantaneous wind-driven air–water interface.The results obtained in this study are not in accord with the conclusions of Okuda et al. that the tangential stress component dominates the wind stress. It is found that prior to the formation of wind waves, the tangential stress contributes the entire wind stress, as expected. With increasing distance downwind, the mean tangential stress level decreases marginally, but as the wave field develops, the total wind stress increases significantly. Thus, the wave form drag, represented by the difference between the total wind stress and the mean tangential stress, also increases systematically with wave development and provides the major proportion of the wind stress once the waves have developed beyond their early growth stage. This scenario reconciles the question of relative importance of normal and tangential stresses at an air–water interface. Finally, consideration is given to the extrapolation of these detailed laboratory results to the field, where the present findings suggest that the sea surface is unlikely to become fully aerodynamically rough, at least for moderate to strong winds.
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GLIMM, TILMANN, and H. G. E. HENTSCHEL. "ON ISOCONCENTRATION SURFACES OF THREE-DIMENSIONAL TURING PATTERNS." International Journal of Bifurcation and Chaos 18, no. 02 (February 2008): 391–406. http://dx.doi.org/10.1142/s0218127408020355.
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We consider three-dimensional Turing patterns and their isoconcentration surfaces corresponding to the equilibrium concentration of the reaction kinetics. We call these surfaces equilibrium concentration surfaces (EC surfaces). They are the interfaces between the regions of "high" and "low" concentrations in Turing patterns. We give alternate characterizations of EC surfaces by means of two variational principles, one of them being that they are optimal for diffusive transport. Several examples of EC surfaces are considered. Remarkably, they are often very well approximated by certain minimal surfaces. We give a dynamical explanation for the emergence of Scherk's surface in certain cases, a structure that has been observed numerically previously in [De Wit et al., 1997].
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Lomonaco, Quentin, Karine Abadie, Jean-Michel Hartmann, Christophe Morales, Paul Noël, Tanguy Marion, Christophe Lecouvey, Anne-Marie Papon, and Frank Fournel. "Soft Surface Activated Bonding of Hydrophobic Silicon Substrates." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1601. http://dx.doi.org/10.1149/ma2023-02331601mtgabs.
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Surface Activated Bonding (SAB) is interesting for strong silicon to silicon bonding at room temperature without any annealing needed, afterwards (1). Although it is a well-known technique, the activation step, in particular, is scarcely documented. This paper offers insights about the impact of soft activation parameters on the amorphous region at the bonding interface. In addition, the adherence energy of hydrophobic silicon bonding with SAB is quantified to better understand bonding mechanisms. With very low dose and acceleration activation parameters, the surface preparation prior to bonding becomes of paramount importance. Indeed, the silicon native oxide is typically removed during the activation step. The thin amorphous silicon region is a side effect of this singular surface preparation(2). In order to work around this potential roadblock, we used instead hydrophobic surface preparation to remove the native oxide, before entering into the activation step. Two types of preparation were evaluated in this study. First, a standard “HF-Last” chemical treatment was used on standard silicon wafers. This treatment removed the silicon native oxide and passivated the surface with Si-H and, to a lesser extent, Si-F bonds (3). We otherwise used epitaxy-reconstructed silicon wafers with fully hydrophobic surfaces (4). Silicon native oxide was removed thanks to an ultra-pure H2 bake at 1100°C, 20 Torr for 2 minutes in an epitaxy chamber. Then, several tens of nm of Silicon were deposited at 950°C to obtain, after another H2 bake, a silicon surface fully passivated by hydrogen atoms with atomically smooth terraces and mono-atomic step edges. Our EVG®ComBond® bonding tool, operating under ultra-high vacuum (UHV), is equipped with an accelerated argon ion beam to perform the activation step. The softest functional settings, on our set up, are 50V (acceleration) and 26 mA (dose). After beam initialization, the two sets of substrates pass through the activation chamber. Activated substrates are then transferred to the bonding chamber within 5 minutes of handling. The exposure time in the activation chamber was evaluated, the aim being to remove adsorbed hydrogen atoms on the silicon surface without any amorphous silicon generation. Different characterization techniques such as transmission electron microscopy or FTIR-MIR were used to quantify the amorphous layer formation and the potential Si-H bonds remaining (after activation). The adherence energy of the bonded pair was measured by a double cantilever beam method under prescribed displacement control in anhydrous atmosphere (5). Figure 1 shows the adherence energy (Gc=2γc) in mJ/m² as a function of activation exposure time with soft activation parameters for both wafer preparations. The 0s reference bonding was conducted without passing through the activation module. We then had very low adherence energies, around 50 mJ/m², as expected for standard hydrophobic silicon wafer bonding under UHV (6). Upon Ar+ exposure, behaviors were very different depending on surface preparation. The adherence energy barely increased with the Ar+ exposure time for “HF-Last” surfaces. Meanwhile, even 1s of exposure to Ar+ had a definite impact on the adherence energy of epi-reconstructed, atomically smooth silicon surfaces, which was definitely higher. The maximum difference between both wafer preparations occurred for 30 up to 60 seconds exposure times. This indicate a change in the bonding mechanism as the comparatively high roughness of the “HF-Last” silicon wafer started to be counter-balanced by activation. The experimental set up, the manufacturing process, as well as further characterizations will be presented. Cross-sectional TEM imaging of the bonding interface, FTIR-MIR and AFM measurements after surface preparation will help us better understand the specificities of such soft activation process on the SAB of hydrophobic surfaces. The impact of the amorphous silicon layer on bonding will be discussed. Suga T et al. STRUCTURE OF A1-A1 A N D A1-Si3N4 INTERFACES BONDED AT ROOM TEMPERATURE BY MEANS OF THE SURFACE ACTIVATION METHOD. Acta Metallurgica et Materialia 1992. Takagi H et al. Surface activated bonding of silicon wafers at room temperature. Appl Phys Lett. 1996. Abbadie A et al. Low thermal budget surface preparation of Si and SiGe. Appl Surf Sci. 2004. Sordes D et al. Nanopackaging of Si(100)H Wafer for Atomic-Scale Investigations. 2017. Maszara WP et al. Bonding of silicon wafers for silicon‐on‐insulator. J Appl Phys. 15 nov 1988;64(10):4943-50. Tong QY et al. The Role of Surface Chemistry in Bonding of Standard Silicon Wafers. J Electrochem Soc. 1997. Figure 1
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Olejnik, Adrian, Michal Sobaszek, Maria Brzhezinskaya, Mateusz Ficek, and Robert Bogdanowicz. "Electrochemistry and Electronic Structure of the Deuterium-Grown Boron-Doped Diamond Interfaces." ECS Meeting Abstracts MA2023-02, no. 57 (December 22, 2023): 2784. http://dx.doi.org/10.1149/ma2023-02572784mtgabs.
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Integration of the first principles quantum mechanical simulations with electrochemistry represents a difficult research area due to the complexity and large size of real systems and computational limitations. On the one hand it is highly desirable to be able to predict electrochemical properties of materials and systems from simulations to limit the money expenditure for experimental work and accelerate applications [1]. On the other hand, utilization of ab-initio simulations to understand the experimentally observed phenomena is also required to embed them into a solid theoretical framework. To fulfill this task, several multiscale approaches are used with the density functional theory (DFT) being fundamental tool for investigation of electronic structure. DFT results can be further extended to build forcefields used in molecular dynamics (MD) [2] for larger scale simulations and non-equillibrium Green's functions for investigations of electronics and spintronics of nanodevices [3]. Semiconductor electrochemistry is one of the most important areas to explore this experiment-theory interface because of the necessity to develop new materials for photovoltaics, photoelectrochemistry, energy storage and conversion. The purpose of the following talk is to show the power of this paradigm by elucidation of the deuterium-grown boron doped diamond (BDD-D) material [4]. A brief introduction to the material synthesis, chemical and physical properties is provided exploiting the synchrotron data of X-Ray absorption spectroscopy and X-Ray photoelectron spectroscopy. Then, a strong emphasis is put into merging the (photo)electrochemical data with the first principle results for better understanding of charge transfer phenomena in the nanoscale. Specifically, DFT calculations of projected local density of states clearly show the presence of highly occupied surface states on the (111) plane of BDD-D in contrast to its standard hydrogen-grown counterpart (BDD-H). The resulting surface states are capable of photocurrent generation in the visible light, which is strongly magnified in BDD-D. Moreover, photoelectrochemical measurements evidenced that photocurrents can be positive or negative depending on the bias - despite BDD being a p-type semiconductor. These confirm a profound role of surface states in the semiconductor electrochemistry and capability of photoinduced charge transfer in the modified materials. The proposed picture shines some new light on the commonly established paradigm of band bending as the key factor driving surface properties of the nanodiamond surfaces [5]. Figure. SEM images of a) BDD@D and b) BDD@H; c) grain size distribution among two samples; d) XRD patterns of the diamond films deposited in the D2/CH4 and H2/CH4 gas mixtures. Reflections at 2θ around 44°, 75°, and 91° correspond to the (111), (220), and (311) diamond lattice planes, respectively. Doubling of the reflections is related to the presence of Kα1 and Kα2 wavelengths in the X-ray radiation [4]. Acknowledgements: M.S., M.B., and M.F. thank Helmholtz-Zentrum Berlin (HZB) for the allocation of synchrotron radiation beamtime at HZB (Germany). M.S. gratefully acknowledges the financial support of these studies from the Gdansk University of Technology through the DEC-02/2021/IDUB/ II.1/AMERICIUM grant under the Americium – “Excellence Initiative – Research University” program. R.B. acknowledges the funding from the National Science Centre, Poland under the OPUS call in the Weave programme (Project number: 2021/43/I/ST7/03205). References: [1] Zhao, Shuangliang, et al. "Unified framework of multiscale density functional theories and its recent applications." Advances in Chemical Engineering. Vol. 47. Academic Press, 2015. 1-83. [2] Le, Jia-Bo, and Jun Cheng. "Modeling electrochemical interfaces from ab initio molecular dynamics: water adsorption on metal surfaces at potential of zero charge." Current Opinion in Electrochemistry 19 (2020): 129-136. [3] Datta, Supriyo. Electronic transport in mesoscopic systems. Cambridge university press, 1997. [4] Sobaszek, Michał, et al. "Highly Occupied Surface States at Deuterium‐Grown Boron‐Doped Diamond Interfaces for Efficient Photoelectrochemistry." Small (2023): 2208265. [5] Kono, Shozo, et al. "Carbon 1s X-ray photoelectron spectra of realistic samples of hydrogen-terminated and oxygen-terminated CVD diamond (111) and (001)." Diamond and Related Materials 93 (2019): 105-130. Figure 1
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Kim, Kyung Sung, Moo Hyun Kim, and Jong-Chun Park. "Development of Moving Particle Simulation Method for Multiliquid-Layer Sloshing." Mathematical Problems in Engineering 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/350165.
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The mixed oil and gas including water and sand are extracted from well to offshore structure. This mixed fluid must be separated for subsequent processes by using wash tanks or separators. To design such a system, a proper numerical-prediction tool for multiphase fluids is required. In this regard, a new moving particle simulation (MPS) method is developed to simulate multiliquid-layer sloshing problems. The new MPS method for multifluid system includes extra search methods for interface particles, boundary conditions for interfaces, buoyancy-correction model, and surface-tension model for interface particles. The new particle interaction models are verified through comparisons with published numerical and experimental data. In particular, the multiliquid MPS method is verified against Molin et al’s (2012) experiment with three liquid layers. In case of excitation frequency close to one of the internal-layer resonances, the internal interface motions can be much greater than top free-surface motions. The verified multiliquid MPS program is subsequently used for more nonlinear cases including multichromatic multimodal motions with larger amplitudes, from which various nonlinear features, such as internal breaking and more particle detachment, can be observed. For the nonlinear case, the differences between with and without buoyancy-correction and surface-tension models are also demonstrated.
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Soligo, Giovanni, Alessio Roccon, and Alfredo Soldati. "Breakage, coalescence and size distribution of surfactant-laden droplets in turbulent flow." Journal of Fluid Mechanics 881 (October 24, 2019): 244–82. http://dx.doi.org/10.1017/jfm.2019.772.
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In this work, we compute numerically breakage/coalescence rates and size distribution of surfactant-laden droplets in turbulent flow. We use direct numerical simulation of turbulence coupled with a two-order-parameter phase-field method to describe droplets and surfactant dynamics. We consider two different values of the surface tension (i.e. two values for the Weber number, $We$, the ratio between inertial and surface tension forces) and four types of surfactant (i.e. four values of the elasticity number, $\unicode[STIX]{x1D6FD}_{s}$, which defines the strength of the surfactant). Stretching, breakage and merging of droplet interfaces are controlled by the complex interplay among shear stresses, surface tension and surfactant distribution, which are deeply intertwined. Shear stresses deform the interface, changing the local curvature and thus surface tension forces, but also advect surfactant over the interface. In turn, local increases of surfactant concentration reduce surface tension, changing the interface deformability and producing tangential (Marangoni) stresses. Finally, the interface feeds back to the local shear stresses via the capillary stresses, and changes the local surfactant distribution as it deforms, breaks and merges. We find that Marangoni stresses have a major role in restoring a uniform surfactant distribution over the interface, contrasting, in particular, the action of shear stresses: this restoring effect is proportional to the elasticity number and is stronger for smaller droplets. We also find that lower surface tension (higher $We$ or higher $\unicode[STIX]{x1D6FD}_{s}$) increases the number of breakage events, as expected, but also the number of coalescence events, more unexpected. The increase of the number of coalescence events can be traced back to two main factors: the higher probability of inter-droplet collisions, favoured by the larger number of available droplets, and the decreased deformability of smaller droplets. Finally, we show that, for all investigated cases, the steady-state droplet size distribution is in good agreement with the $-10/3$ power-law scaling (Garrett et al., J. Phys. Oceanogr., vol. 30 (9), 2000, pp. 2163–2171), conforming to previous experimental observations (Deane & Stokes, Nature, vol. 418 (6900), 2002, p. 839) and numerical simulations (Skartlien et al., J. Chem. Phys., vol. 139 (17), 2013).
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TONG, S. Y., HUA LI, and H. HUANG. "SURFACE CRYSTALLOGRAPHY BY INVERTING DIFFRACTION SPECTRA." Surface Review and Letters 01, no. 02n03 (August 1994): 303–18. http://dx.doi.org/10.1142/s0218625x9400031x.
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New ideas on how to invert electron diffraction spectra to produce the atomic coordinates of surface region atoms are reviewed in this article. Some of the ideas are borrowed from optical holography while others are invented to deal with the strong multiple scattering and angular anisotropies present in electron diffraction in solids. The examples and references given in this and the accompanying two articles (by Heinz et al. and Wei et al. respectively) demonstrate that surface crystallography by data inversion is a viable method for a number of commonly used surface diffraction techniques.
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Das, Prodip. "(Invited, Digital Presentation) Tuning Gas-Diffusion-Layer Surface Wettability for Polymer Electrolyte Fuel Cells." ECS Meeting Abstracts MA2022-01, no. 38 (July 7, 2022): 1709. http://dx.doi.org/10.1149/ma2022-01381709mtgabs.
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In the present scenario of a global initiative toward securing global net-zero by mid-century and keeping 1.5 degrees within reach, polymer-electrolyte fuel cells (PEFCs) are considered to play an important role in the energy transition, particularly for the decarbonization of transit buses, trucks, rail transport, ships and ferries, and the residential heating sector. However, PEFCs are not economically competitive with the internal combustion engine powertrains [1]. Moreover, their durability standards in widely varying conditions have yet to be established and water management remains a critical issue for performance degradation and durability [1-3]. Thus, the mission of my research team is to conduct original research to make PEFCs economically viable and optimize their performance and durability [4,5]. In this talk, I will highlight our research on PEFC’s gas diffusion layer (GDL), as its interfaces with the flow channel and microporous layer play a significant role in water management. This research was aimed at selectively modifying GDL surfaces with a hydrophobic pattern to improve water transport and water removal from flow channels; thus, improving the durability and performance of PEFCs. Sigracet® GDLs were used as a base substrate and two different monomers, polydimethylsiloxane (PDMS) added with fumed silica (Si) and fluorinated ethylene propylene (FEP) were used to print a selective pattern on the GDL surfaces [6]. Both the additive manufacturing and spray coating techniques were utilized for creating the hydrophobic pattern on the GDL surfaces. The results of this study demonstrated a novel but simple approach to tune GDL surfaces with selective wetting properties and superhydrophobic interfaces that would enhance water transport. I will discuss some of these results and highlight how these results will benefit the water management of next-generation high-power PEFCs. This work was funded by the Engineering and Physical Sciences Research Council (EP/P03098X/1) and the STFC Batteries Network (ST/R006873/1) and was supported by SGL Carbon SE (www.sglcarbon.com). References [1] A.Z. Weber et al., "A critical review of modeling transport phenomena in polymer electrolyte fuel cells," J. Electrochem. Soc., vol. 161, pp. F1254-F1299, 2014. [2] A.D. Santamaria et al., "Liquid-water interactions with gas-diffusion layers surfaces," J. Electrochem. Soc., vol. 161, pp. F1184-F1193, 2014. [3] P.K. Das and A.Z. Weber, "Water management in PEMFC with ultra-thin catalyst-layers," ASME 11th Fuel Cell Science, Engineering and Technology Conference, Paper No. FuelCell2013-18010, pp. V001T01A002, 2013. [4] L. Xing et al., "Membrane electrode assemblies for PEM fuel cells: A review of functional graded design and optimization," Energy, vol. 177, pp. 445-464, 2019. [5] L. Xing et al., "Inhomogeneous distribution of platinum and ionomer in the porous cathode to maximize the performance of a PEM fuel cell," AIChE J., vol. 63, pp. 4895-4910, 2017. [6] D. Thumbarathy et al., "Fabrication and characterization of tuneable flow-channel/gas-diffusion-layer interface for polymer electrolyte fuel cells," J. Electrochem. Energy Convers. Storage, vol. 17, pp. 011010, 2020.
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Boz, Emre Burak, Ronald de Bruijne, and Antoni Forner-Cuenca. "Exploring Conductive Polymer Coatings to Target Reaction Selectivity in Aqueous All-Iron Redox Flow Batteries." ECS Meeting Abstracts MA2023-02, no. 59 (December 22, 2023): 2888. http://dx.doi.org/10.1149/ma2023-02592888mtgabs.
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An energy grid that relies on wind and solar farms requires the installation of large-scale energy storage systems to balance their fluctuating output. Especially for developing countries, wide adoption of renewables is coupled to progress in sustainable and cost-effective storage technologies.1 From this perspective, aqueous all-iron redox flow batteries (AIRFBs) stand out as a promising technology, owing to the earth-abundance and low-cost of iron, along with its environmental and operational safety. In this battery, iron is utilized in its three oxidation states (Fe0, Fe2+ and Fe3+) and the negative electrode leverages the iron plating/stripping reactions to sustain charge and discharge. However, the standard potential of iron plating is 0.44 V below the hydrogen evolution reaction (HER), which causes faradaic losses during the charging stage and increases the pH of the solution.2 The catalytic activity of iron towards hydrogen evolution and the precipitation of iron hydroxide at pH above 3.5 further complicates the operation of AIRFBs. Thus, the reaction selectivity of the negative electrode should be targeted to improve the operational time and efficiency. So far, research has focused on electrolyte engineering to hinder adsorption of hydrogen on surfaces or excluding water from the solvent shell of iron.2,3 Alternatively, interfacial engineering of electrode surfaces can be a promising strategy to tune the reaction selectivity, given that hydrogen adsorption and iron nucleation are interfacial phenomena. The challenge here is to prevent a new interface from being created by the plated iron as that would render the modified interface obsolete. We hypothesize that polymeric layers where iron deposition can take place within or underneath the polymer (akin to a solid electrolyte interphase of a Li-ion battery anode) would preserve the HER-inhibiting characteristics of the surface. Here, we propose conductive polymer interfaces to target reaction selectivity during the iron plating reaction. Conductive polymers have been used to engineer HER-inhibiting interfaces and as corrosion protection layers for metals.4,5 Furthermore, they can be conformally coated on porous electrodes, enabling their use in flow reactors.6 We selected two conductive polymer systems: poly(pyrrole) (PPy) owing to its iron-coordinating nitrogen moieties and poly(3,4-ethylenedioxythiophene) (PEDOT) owing to its high conductivity and stability.7 Furthermore, we employed three counterions of different size, chlorine (Cl-), p-toluenesulfonate (pTS-) and poly(styrenesulfonate) (PSS-), to direct the morphology of the coating, resulting in six different polymer systems. On glassy carbon electrodes, all polymers significantly hinder HER at potentials as low as -1.5 V (vs Ag/AgCl) where heavy bubble formation is observed on bare electrodes (Figure 1). To assess the selectivity of the coatings on carbon paper substrates, we are developing an electrochemical protocol with successive plating/stripping cycles that is representative of battery operation. Preliminary results show that all polymer systems hinder the HER, but also the Fe-plating reaction, resulting in lower plating currents than the bare carbon paper electrodes. To validate the methodology, we compare the electrochemically obtained reaction selectivity values with the ones from gravimetric analysis. The ideal polymeric interfaces should inhibit the HER without largely impacting the Fe-plating kinetics, which motivates research into the relationship between the coating thickness, conductivity, and the faradaic efficiency. To understand the plating morphology on polymeric coatings, we investigate the spatial distribution of iron on the surface and the cross-section of plated electrodes using microscopic methods. Hydrogen evolution and limited durability due to complex plating reactions hamper the broad implementation of all-iron redox flow batteries and we hope to tackle these challenges through interfacial electrode engineering. References Rahman et al., in Renewable Energy and Sustainability, Elsevier, 2022, pp. 347–376. Hawthorne et al., J. Electrochem. Soc. 2014, 162, A108. Liu et al., ACS Cent. Sci. 2022, 8, 729. Tian et al., J. Electrochem. Soc. 2013, 161, E23. Deshpande et al., J Coat Technol Res 2014, 11, 473. Boz et al., Adv Materials Inter 2023, 2202497. Mao et al., Energy Environ. Sci. 2011, 4, 3442. Figure 1
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Zazpe, Raul, Hanna Sopha, Mouli Thalluri, Ludek Hromadko, Jhonatan Rodriguez Pereira, Martina Rihova, and Jan M. Macak. "(Invited) Atomic Layer Deposition on 1D Nanomaterials for Various Applications." ECS Meeting Abstracts MA2023-02, no. 29 (December 22, 2023): 1441. http://dx.doi.org/10.1149/ma2023-02291441mtgabs.
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One-dimensional nanomaterials – materials with one dimension outside the nanoscale, further noted as 1D NMs – represent a class of very important nanomaterials with continuously increasing importance. Due to their intrinsic features, unique properties and diversity of functionalities, they count among the most widely studied materials nowadays. While considerable research efforts have been spent to synthesize various 1D NMs (e.g. nanopores, nanotubes or nanofibers), limited efforts have been devoted to surface modification and property tailoring of these materials. However, it is their surface that comes into direct contact with various media (air, gases, liquids, solids) and influences the reactivity, stability and biocompatibility of these materials. The surface and aspect ratio (defined as their diameter to length ratio) influence the performance of these materials in various applications. Considering these facts, it is more relevant to tailor the surface of these materials and to be able to influence their properties and reactivity at the nanoscale, rather than to deal with tailoring their own bulk material composition. The focus of this presentation is on the modification of two types of 1D nanomaterials – nanotubes and nanofibers. Numerous techniques can be utilized for this purpose, such as for example wet chemical or physical deposition techniques. However, it is only the Atomic Layer Deposition (ALD) that is capable of really uniform and homogenous coating of these 1D nanomaterials, in particular those of very high-aspect ratio. The presentation will be mainly focused on modification of TiO2 nanotube layers and various nanofibers of different aspect ratios via ALD. Experimental details and some very recent application examples in photocatalysis, catalysis, sensors, batteries, nanorobots, etc. [1-11] and structural characterizations of these modified materials will be discussed. Sopha et al (2017), Appl. Mater. Today, 9, 104. Sopha et al. (2018), Electrochem. Commun.,97, 91. Ng et al. (2017), Adv. Mater. Interfaces, 1701146. Dvorak et al. (2019), Appl. Mater. Today, 14, 1. Sopha et al. (2019), FlatChem 17, 100130. Motola et al. (2019), Nanoscale 11, 23126. Ng et al. (2020), ACS Appl. Mater. Interfaces, 12, 33386. Motola et al. (2020) ACS Appl. Bio Mater. 3, 6447. Rihova & M. Knez & J. M. Macak et al. (2021), Nanoscale Adv., 3, 4589 Galstyan, T. Djenizian, J. M. Macak (2022), Appl. Mater. Today, 29, 101613 Villa & M. Pumera & J. M. Macak et al. (2022), Small, 2106612
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Ngene, Peter. "Interface Induced Fast Ion Conduction in Complex Hydride/Oxide Nanocomposites: Interplay between Hydride and Oxide Properties." ECS Meeting Abstracts MA2023-02, no. 5 (December 22, 2023): 886. http://dx.doi.org/10.1149/ma2023-025886mtgabs.
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Solid-state electrolytes are crucial for next generation batteries with high energy density, long lasting and improved safety. The compatibility of most solid electrolytes with metallic anodes such as Li and Na metals, and cathodes such as sulfur, makes them suitable for high-capacity batteries (e.g., Li-S). They also address the safety concerns of current batteries by eliminating the flammable organic solvents in liquid electrolytes and by preventing/limiting dendrite formation. The lithium and sodium containing complex metal hydrides (e.g., LiBH4, NaBH4, LiCB11H12) have recently gained attention as solid-state electrolyte. They show high ionic conductivities but only at elevated temperatures (typically above 110 °C). Extending the high ionic conductivities to ambient temperatures is pivotal to the application of this fascinating class of solid electrolytes [1]. In this contribution, we will use LiBH4 and NaBH4 as examples to show that the ionic conductivities of complex hydrides can be greatly enhanced through interface effects resulting from the formation of nanocomposites with metal oxides. This strategy can lead to several orders of magnitude increase in the room temperature ionic conductivity [2]. Using DSC, DRIFT, solid-state NMR, and XRS (Xray Raman scattering), I will discuss how nanocomposite formation and presence of interfaces modifies either the phase stability, the defect concentration and/or leads to the formation of tertiary phase, and thereby increase profoundly the ion mobility of the complex hydrides. Systematic studies with different oxide nanoscaffolds and surface modified metal oxides, reveal that these effects can be optimized by tuning/engineering the nanostructure and interfaces in the nanocomposites. [3-4]. We will show that the effects also depend on a complex interplay between the stability of the metal hydride and surface properties of the metal oxide. Finally, the performance of some of the nanocomposite electrolytes in all-solid-state batteries, will be highlighted [5] References [1] L.M de Kort, P. Ngene et al. J. Journal of Alloys and Compounds 901 (2022) 163474 [2] D. Blanchard et al., Advanced Functional Material. 25 (2015), 182. [3] P. Ngene et al. Physical Chemistry Chemical Physics 21 (40), 22456-22466 [4] L.M de Kort, P. Ngene et al. Journal of Materials Chemistry A 8.39 (2020): 20687-20697 [5] D. Blanchard et al, J. Electrochem. Soc. (2016).
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Hebert, Kurt. "Morphological Instability of Lithium Electrodeposition Due to Stress-Driven Interface Diffusion." ECS Meeting Abstracts MA2022-01, no. 1 (July 7, 2022): 39. http://dx.doi.org/10.1149/ma2022-01139mtgabs.
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Morphological instability of the lithium-electrolyte interface is a critical problem limiting the development of lithium-metal negative electrodes for batteries. At high current densities approaching the diffusion-limited current density, dendrites form due to depletion of Li+ ions near the electrode surface (1). At lower current densities, unstable deposition produces whiskers (2). Whiskers are separated by typically several micrometers, and in contrast to dendrites grow by addition of Li atoms to their base or "root" (3). Experimental evidence indicates that whisker growth is fed by large-scale interface or grain boundary diffusion, and that whiskers relieve compressive stress in the metal generated by electrodeposition (4-7). The present study proposes that Li electrodeposition is destabilized by interface diffusion driven by compressive stress due to incorporation of Li atoms at grain boundaries. The competition between stress and stabilizing surface energy effects generates a surface pattern which determines (in part) whisker sites. A morphological instability model is formulated based on the Asaro-Tiller-Grinfel'd (ATG) surface instability on elastically stress solids (8). The model applies to deposits less than 1 micron thick for which elastic deformation is expected to dominate (9,10). The Li electrode is depicted by a three-layer elastic model consisting of a stress-free substrate (current collector) layer, a Li layer with uniform diffusion-induced in-plane stress, and top layer. The top layer can simulate submicron thickness solid-electrolyte interface (SEI) layers, or macroscopically thick polymer separators and solid electrolytes. The Li-top layer interface deforms by diffusion. Out-of-plane normal stress is included to simulate the effect of applied stress on the instability (11,12). For model calculations, the interface stress was estimated from neutron-depth-profiling measurements of Li diffusion into Cu current collectors (13). The measured Li incorporation was found to be consistent with a whisker spacing of several microns, in agreement with experimental results (3,6,14). Calculations showed that the instability is inhibited significantly by the use of substrates with elastic modulus much greater than that of Li. This substrate stiffness effect is consistent with experimental observations of Sn whiskers (15). The effect of a stress-free SEI layer on the instability was found to be negligible, due to its small thickness. Whisker growth was suppressed by macroscopically thick top layers with elastic modulus at least 10 times that of Li. No significant whisker inhibition was found at applied stress levels of ~ 1 MPa, which are found experimentally to stabilize deposition in Li films significantly exceeding 1 micron thickness (11,12). This effect may be due to an instability associated with viscoplastic rather than elastic deformation (16). REFERENCES P. Bai et al., Energy Environ. Sci., 9, 3221(2016). L Frenck et al., Front. Energy Res., 7, 115 (2016) A. Kushima et al., Nano Energy, 32, 271 (2017). J. H. Cho et al., Energy Storage Mater., 24, 281 (2020). X. Wang et al., Nat. Energy, 3, 227 (2018). A. A. Rulev et al., J. Phys. Chem. Lett., 11, 10511 (2020). E. Chason et al., Prog. Surf. Sci., 88, 103 (2013). B. J. Spencer et al., J. Appl. Phys., 73, 4956 (1993). C. Xu et al., Proc. Nat. Acad. Sci., 114, 57 (2017). L. Q. Zhang et al., Nat. Nanotechnol., 15, 94 (2020). A. J. Louli et al., J. Electrochem. Soc., 166, A1291 (2019). K. L. Harrison et al., ACS Appl. Mater. Interfaces, 13, 31668 (2021). S. Lv et al., Nat. Commun., 9, 2152 (2018). J. Steiger et al., J. Power Sources, 261, 112 (2014). B. Hutchinson et al., Mater. Sci. Forum, 467-470, 465 (2004). S. Narayan and L. Anand, J. Electrochem. Soc., 167, 040525 (2020).
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Yang, Keun-Hyeok. "Shear Stress-Relative Slip Relationship at Concrete Interfaces." Advances in Materials Science and Engineering 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/6475161.
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This study develops a simple and rational shear stress-relative slip model of concrete interfaces with monolithic castings or smooth construction joints. In developing the model, the initial shear cracking stress and relative slip amount at peak stress were formulated from a nonlinear regression analysis using test data for push-off specimens. The shear friction strength was determined from the generalized equations on the basis of the upper-bound theorem of concrete plasticity. Then, a parametric fitting analysis was performed to derive equations for the key parameters determining the shapes of the ascending and descending branches of the shear stress-relative slip curve. The comparisons of predictions and measurements obtained from push-off tests confirmed that the proposed model provides superior accuracy in predicting the shear stress-relative slip relationship of interfacial shear planes. This was evidenced by the lower normalized root mean square error than those in Xu et al.’s model and the CEB-FIB model, which have many limitations in terms of the roughness of the substrate surface along an interface and the magnitude of equivalent normal stress.
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Bulle-Lieuwma, C. W. T., A. F. de Jong, and D. E. W. Vandenhoudt. "Investigation of Si/CoSi2/Si(001) interfaces formed by high-dose Co implantation using HREM and image simulations." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 344–45. http://dx.doi.org/10.1017/s0424820100174850.
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Cobaltdisilicide has been the subject of much study, because of the good lattice matching with Si, its low resistivity, and the formation of atomically abrupt interfaces. Hetero-epitaxial Si/ CoSi2/Si structures are of interest due to their potential application as metal and permeable base transistors. We have synthesized mesotaxial CoSi2 films of aligned orientation by high-dose implantation of Co+ ions into Si (001) substrates followed by a high-temperature treatment of 30 minutes at 1000 °C. The Si wafers were implanted with 170 keV Co+ ions, with doses of 1 to 2 × 1017 Co+/cm2 , at an ion current density of 11 μA/cm2. The atomic structure of the CoSi2/ Si (001) interface has been investigated by high-resolution microscopy (HREM) combined with image simulations. The electronic properties of the CoSi2 films, such as the Schottky barrier height between the metal and the semiconductor, may be influenced by the atomic structure of the interface. Moreover, detailed knowledge of the atomic interface structure can give insight into mechanisms of silicide growth. Recently, Loretto et al. have shown that the structure of a CoSi2 /Si (001) interface grown by molecular beam epitaxy (MBE) is a 2×1 reconstruction of silicon dimers with bond length 0.23 nm, similar to the Si (001) 2×1 surface. This model (see fig. 1a) differs from that of Cherns et al. concerning NiSi2/Si (001), by the presence of an extra row of atoms at the interface. The additional Si atoms can form dimer chains, reducing the number of dangling bonds. This interface model projected along [110], is shown in Fig. 1a (see lower interface). The upper interface can be considered as a projection of the same structure along [10] .
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Fujii, Nobutoshi, Shunsuke Furuse, Hirotaka Yoshioka, Naoki Ogawa, Taichi Yamada, Takaaki Hirano, Suguru Saito, Yoshiya Hagimoto, and Hayato Iwamoto. "(Invited) Bonding Strength of Cu-Cu Hybrid Bonding for 3D Integration Process." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1583. http://dx.doi.org/10.1149/ma2023-02331583mtgabs.
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Introduction Cu-Cu hybrid bonding is a significant technology in the manufacture of 3D stacked semiconductor devices and is indispensable for the integration of 3D heterogeneous stacked packages.1 A process is used to thin the bonded semiconductor during 3D stacking integration, but delamination can occur when the bonding strength of the bonded interface is insufficient. Therefore, the bonding strength is a key factor in the 3D stacked integration process, and mechanisms for improving the strength have been thoroughly investigated. Cu-Cu hybrid bonding strength During Cu-Cu hybrid bonding, the bonding strength between bonded wafers, which is a crucial factor, is complicated to describe because of the various materials contained in the bonding interface. Because the bonding interface includes not only Cu/Cu and dielectric/dielectric films, but also Cu/dielectrics as a result of the misalignment of Cu pads, the strength of the Cu-Cu hybrid bond needs to comprehensively account for these interfaces. We investigated the relationship between the bonding strength and amount of misalignment using patterned Si substrates that were bonded after intentionally being aligned with an offset and thermally annealed. Although the bonding strength before annealing was confirmed to decrease lineally depending on the amount of misalignment, the wafers showed a different behavior after annealing in the region where the amount of misalignment was low. Simulation calculations elucidated the behavior of the overall bonding strength. When a Cu pad with a large recess contacted the opposing Cu pad, an uneven amount of pressure was generated between their contact surfaces because of the thermal expansion produced by the annealing. An area with very low pressure was also found between the surfaces, and extremely little or no diffusion occurred in this area.2 This phenomenon was not observed in a case where the amount of recess was small in both the experiments and simulation calculations, which showed linear relationships dependent on the misalignment after annealing. This study determined the misalignment dependence of the bonding strength after annealing considering the recess of the Cu pad, and an integrated model of the comprehensive bonding strength that included three interfaces involved in the Cu-Cu hybrid bonding could be presented. Improvement of bonding strength between dielectric films We are also continuing to study ways to improve the bonding strength of the interface between the dielectrics films that exist in the interfaces of a Cu-Cu hybrid bond. Elucidating the mechanism of strength generation would offer a guideline to improve the bonding strength. The dielectric films are bonded using a dehydration condensation reaction on the plasma-activated surface by thermal annealing. This bonding process has been widely studied from the perspective of the amount of surface Si-OH by considering the activation method and condition, type of dielectrics, and flatness of the surface. Because few investigations have considered factors other than the bonding interfaces, we focused on the influence of the H2O contained in the dielectric film to be bonded and investigated the relationship between the amount of H2O in the film and the bonding strength. The deposition conditions of the dielectric films produced using Plasma Enhanced Chemical Vapor Deposition (PE-CVD) were varied to prepare five types of films that contained various amounts of H2O. After CMP treatment of each film, the surface roughness and amount of Si-OH were measured, and it was confirmed that there was no significant difference. When the bonding strength was obtained by bonding using these films and plotted against the amount of H2O, it was found that the bonding strength was dependent on the amount of H2O. In addition, after being bonded and annealed, it was confirmed that the expansion of the dielectric film depended on the amount of H2O, as seen in cross-sectional STEM images of the interface. An investigation of the mechanism for this phenomenon suggested that the bonding strength was increased by filling the gap in the bonding interface through the expansion of the film. This study suggested that filling up the gap in the interface would be one approach for improving the bonding strength. These results offer a deep understanding of the mechanism for the bonding strength of Cu-Cu hybrid bonds and will contribute to the development of 3D stacking technology in the future. References [1] P. Ramm, et al., “Handbook of Wafer Bonding”, Wiley-VCH Verlag & Co., 2012 [2] S. Furuse, et al., “Behavior of Bonding Strength on Wafer to Wafer Cu-Cu Hybrid Bonding”, ECTC Proc., pp591, 2023
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Wissink, J. G., H. Herlina, Y. Akar, and M. Uhlmann. "Effect of surface contamination on interfacial mass transfer rate." Journal of Fluid Mechanics 830 (September 29, 2017): 5–34. http://dx.doi.org/10.1017/jfm.2017.566.
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The influence of surface contamination upon the mass transfer rate of a low diffusivity gas across a flat surface is studied using direct numerical simulations. The interfacial mass transfer is driven by isotropic turbulence diffusing from below. Similar to Shen et al. (J. Fluid Mech., vol. 506, 2004, pp. 79–115) the surface contamination is modelled by relating the normal gradient of the horizontal velocities at the top to the horizontal gradients of the surfactant concentrations. A broad range of contamination levels is considered, including clean to severely contaminated conditions. The time-averaged results show a strong correlation between the gas transfer velocity and the clean surface fraction of the surface area. In the presence of surface contamination the mass transfer velocity $K_{L}$ is found to scale as a power of the Schmidt number, i.e. $Sc^{-q}$, where $q$ smoothly transitions from $q=1/2$ for clean surfaces to $q=2/3$ for very dirty interfaces. A power law $K_{L}\propto Sc^{-q}$ is proposed in which both the exponent $q$ and the constant of proportionality become functions of the clean surface fraction.
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Pellicer, Eva, and Jordi Sort. "(Invited) Mesoporous Metallic Materials Electrodeposited from Polymeric Micelle Assemblies for Energy Applications." ECS Meeting Abstracts MA2023-02, no. 21 (December 22, 2023): 1287. http://dx.doi.org/10.1149/ma2023-02211287mtgabs.
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The surfactant-assisted electrodeposition is an effective means to obtain high-quality mesoporous materials in a rather simple synthesis approach. Commercial or home-made block copolymers can be dissolved in aqueous media above their critical micelle concentration to serve as a soft template in the so-called electrodeposition from polymeric micelle assemblies or micelle-assisted electrodeposition in short [1]. The nanoscale porosity of the resulting films, which extends throughout the whole surface and entire film thickness, endow them with large surface-to-volume (S/V) ratios. Such large S/V ratios are particularly amenable for (electro)catalytic applications and, whenever the alloy presents ferromagnetic properties, for magnetoelectric purposes. In our group, mesoporous Cu-Ni, Co-Pt, Ni-Pt and Fe-Pt alloys with pore size around 10 nm have been electrodeposited from Pluronic P-123 containing solutions [2-4]. Similarly, mesoporous Ni films with larger pore diameters (25 - 600 nm) have been deposited using custom-made PS-b-P4VP block copolymer micelles [5]. Even, the double template approach can be utilized to obtain, for example, matrices of mesoporous Co-Pt microdisks when the micelle-assisted electrodeposition is performed on optically lithographed substrates [6], or nanoporous Fe-Pd nanowires using anodized alumina and P-123 as hard and soft templates, respectively [7]. The introduction of an equilibration time between electrolyte preparation and deposition has been determined key in some cases to consistently reproduce the films mesoporosity [8]. The electrodeposited mesoporous metallic materials exhibit higher electrocatalytic activity towards hydrogen evolution reaction (HER) in either acid or alkaline media compared to their dense counterparts [3]. In addition, their durability is not severely compromised in spite of the much larger surface exposed to the media. On the other hand, modulation of their magnetic properties with voltage is also possible when these films are electrolyte-gated in aprotic polar solvents like propylene carbonate. The intense electric field strength created at the film / electrolyte interface thanks to the built-in electric double layer allows for tuning of the coercivity (HC) or the saturation magnetization upon voltage application by virtue of different, but often concomitant, mechanisms taking place, like charge carrier accumulation and oxygen migration [6,9]. Variations greater than 30% in HC have been achieved. In this talk I will summarize the main synthesis-wise milestones achieved during the research in the field and the benefits brought by mesoporous alloys to electrocatalysis and magnetoelectricity. [1] C. Li et al. Acc. Chem. Res. 51 (2018) 1764 [2] J. Zhang et al. ACS Appl. Mater. Interfaces 10 (2018) 14877 [3] K. Eiler et al. Appl. Cat. B 265 (2020) 118597 [4] E. Isarain‐Chávez et al. ChemSusChem 11 (2018) 367 [5] R. Fagotto Clavijo et al. Cat. Today, in press. [6] C. Navarro-Senent et al. ACS Appl. Mater. Interfaces 10 (2018) 44897 [7] D. Raj et al. Nanomaterials 13 (2023) 403 [8] C. Navarro-Senent et al. Electrochim. Acta 358 (2020) 136940 [9] C. Navarro-Senent et al. APL Materials 7 (2019) 030701
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Kawaguchi, Tomoya, Vladimir Komanicky, Reshma Rao, Yang Shao-Horn, Yihua Liu, and Hoydoo You. "X-Ray Crystal Truncation Rod Studies of Electrochemical Double Layers." ECS Meeting Abstracts MA2022-02, no. 56 (October 9, 2022): 2168. http://dx.doi.org/10.1149/ma2022-02562168mtgabs.
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Electrochemical double layers (EDL) is traditionally described as diffuse distributions of cations and anions, proposed in Gouy and Chapman (GC) model[1] and further developed extensively over decades largely based on voltammetry measurements. However, the GC model is suspected to break down at large potentials, because it predicts the unlimited rise in differential capacitance. Stern suggested long ago that there should be a layer with a finite ion density, known as ‘Stern layer’[2]. While it is generally accepted that Gouy-Chapman model or its modified versions describe well electrochemical interphase structures, recent studies of Pt(111) surface in CsF solution using a model-independent direct inversion method[3] have shown that Stern layer forms over the large double-layer potential range on Pt(111) surface.[4] In this talk, we present synchrotron x-ray observation of Electrochemical Stern layers on the surfaces of RuO2 single crystals in 0.1 M CsF electrolyte. It is of fundamental importance to study if Stern layer forms on electrode surfaces other than Pt(111). In this case, we will examine RuO2 surfaces and compare the results to that of Pt(111) surface. RuO2 is chosen for several reasons. First, it is a well-studied system because of its oxygen evolution reactions and we are familiar with the structure because of our previous studies.[5,6] Second, it is an oxide with oxygen terminated while Pt is a pure metal. Third, the surfaces of RuO2 are squares or rectangles while that Pt(111) surface is triangles. The Stern layers formed at the interfaces of RuO2 (110) and (100) are compared to the previously reported Stern layer on Pt(111). [4] While the Cs+ density profiles at the potentials close to hydrogen evolution reactions are similar, the hydration layers intervening the surface and the Cs+ layer are significantly denser on RuO2 surfaces than that on Pt(111) surface, reflecting the oxygen termination of RuO2 surfaces. The overall similarities between Stern layers on ruthenium surfaces and platinum surface suggest the universal presence of Stern layers in all well-defined solid-electrolyte interfaces. [1] Bard, A. J.; Faulkner, L. R., Electrochemical methods: fundamentals and applications. 2nd ed.; John Wiley: New York, 2001. [2] Stern, O., The theory of the electrolytic double layer. Zeitschrift Für Elektrochemie 1924, 30, 508. [3] Kawaguchi, T. et al., J. Appl. Cryst., 2018 51, 679. [4] Liu, Y.; Kawaguchi, T.; Pierce, M.S.; Komanicky, V.; You, H., Layering and Ordering in Electrochemical Double Layers, J Phys Chem Lett, 2018, 9, 1265. [5] Y.S. Chu, T.E. Lister, W.G. Cullen, H. You, Z. Nagy, Physical Review Letters 2001, 86, 3364. [6] Rao, R.R. et al., Journal of Physical Chemistry C, 2018, 122, 17802
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Troin, Jean-François. "Nasr J. et Padilla P. (dir.) Interfaces : agricultures et villes à l’Est et au Sud de la Méditerranée Beyrouth, Delta, IFPO, 2004, 429 p." Annales de géographie 654, no. 2 (April 1, 2007): 221. http://dx.doi.org/10.3917/ag.654.0221.
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Noël, Paul, Vincent Larrey, Christophe Morales, Francois Rieutord, Didier Landru, and Frank Fournel. "Infrared Spectroscopy Study of Edge Water Penetration at Hydrophilic Bonding Interface." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1588. http://dx.doi.org/10.1149/ma2023-02331588mtgabs.
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Hydrophilic wafer bonding is a process used to bond two wafers without adding material between the two surfaces. Water has a definite impact both during the bonding (bonding wave propagation, adhesion) (1) and after annealing (mechanical strength of the bonding interface, adherence) (2) during such a process. To have a better understanding of mechanisms ruling direct hydrophilic wafer bonding, it is thus important to quantify the amount of water present at the bonding interface. It is known that water is able to penetrate at the bonding interface at room temperature and 40% relative humidity. This has been demonstrated by analyzing defects with scanning acoustic microscopy (SAM) and from X-Ray Reflectivity (XRR) measurements (3,4). Kinetics observed by Tedjini et al. were consistent with a Lucas-Washburn flow through a one nm gap driven by the capillary forces of the hydrophilic surfaces. Nevertheless, no investigation of this phenomenon was performed using Fourier Transform Infra-Red Multiple Internal Reflection (FTIR-MIR) spectroscopy (5). Infrared spectroscopy of silanols, hydrogen bonded water and free water is well documented (6–8) and provides knowledge about water content and organization at the bonding interface. Here FTIR-MIR spectroscopy yields a direct measurement of the relative amount of water and its structure at the interface. More precisely this study will enable us to compare Si-Si, Si-SiO2 and SiO2-SiO2 water penetration kinetics at a fixed distance from the edge of the bonded substrates. A schematic view of the FTIR-MIR setup is shown in Figure 1 to explain the measurement principle. We report the study of water kinetics penetration at bonding interface by FTIR-MIR characterization. A Gaussian decomposition of the OH stretching absorption band signal allows identifying the contributions of silanols, surface bonded water and free liquid water as shown on Figure 2. The integral of each Gaussian peak is otherwise proportional to the relative amount of water. Surface preparation will be discussed and results compared to other characterizations techniques. REFERENCES Larrey V, Mauguen G, Fournel F, Radisson D, Rieutord F, Morales C, et al. Adhesion Energy and Bonding Wave Velocity Measurements. ECS Transactions. 23 sept 2016;75(9):145-52. Fournel F, Tedjini M, Larrey V, Rieutord F, Morales C, Bridoux C, et al. Impact of Water Edge Absorption on Silicon Oxide Direct Bonding Energy. ECS Transactions. 23 sept 2016;75(9):129-34. Tedjini M, Fournel F, Moriceau H, Larrey V, Landru D, Kononchuk O, et al. Interface water diffusion in silicon direct bonding. Appl Phys Lett. 12 sept 2016;109(11):111603. Rieutord F, Tardif S, Landru D, Kononchuk O, Larrey V, Moriceau H, et al. Edge Water Penetration in Direct Bonding Interface. ECS Trans. 24 août 2016;75(9):163-7. Rochat N, Olivier M, Chabli A, Conne F, Lefeuvre G, Boll-Burdet C. Multiple internal reflection infrared spectroscopy using two-prism coupling geometry: A convenient way for quantitative study of organic contamination on silicon wafers. Appl Phys Lett. 2 oct 2000;77(14):2249-51. Baum M, Rébiscoul D, Juranyi F, Rieutord F. Structural and Dynamical Properties of Water Confined in Highly Ordered Mesoporous Silica in the Presence of Electrolytes. J Phys Chem C. 30 août 2018;122(34):19857-68. Caër SL, Pin S, Esnouf S, Raffy Q, Ph. Renault J, Brubach JB, et al. A trapped water network in nanoporous material: the role of interfaces. Physical Chemistry Chemical Physics. 2011;13(39):17658-66. Davis KM, Tomozawa M. An infrared spectroscopic study of water-related species in silica glasses. Journal of Non-Crystalline Solids. 2 juin 1996;201(3):177-98. Figure 1
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Miller, R. G., C. Q. Bowles, P. L. Gutshall, and J. D. Eick. "The Effects of Ion Sputtering on Dentin and its Relation to Depth Profiling." Journal of Dental Research 73, no. 8 (August 1994): 1457–61. http://dx.doi.org/10.1177/00220345940730081001.
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Characterization of the dentin surface and the dentin/adhesive interface is fundamental to investigations concerning adhesive bonding to dentin. It has been shown that good adhesive bonding depends on both the structure and composition of the dentin surface. A combination of ion sputter etching and Auger electron spectroscopy can be used to obtain surface composition and elemental depth profiles at interfaces. This investigation was conducted to examine the changes induced in human dentin by ion sputtering under conditions commonly encountered during depth profiling. The sputtering was conducted with argon ions at 7.5 keV and an ion flux ranging from 1018-1019 ions/m 2s. The amount of material sputtered was calculated from profilometer measurements of the sample surface. The surface composition was monitored by Auger electron spectroscopy. The results indicate that, under these conditions, collagen was removed at a much faster rate than hydroxyapatite, causing the surface composition of dentin to change during the sputtering process. The sputter yields for hydroxyapatite and collagen were found to be 5 and 28 atoms/ion, respectively, at a sputter angle of 45°. At a sputter angle of 29°, the yields were 2 and 25 atoms/ion, respectively. Both the changes in composition of dentin and the measured sputter rates are in agreement with the behavior predicted by a theoretical model for two phase materials (Blaise, 1978; Blaise et al., 1978).
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Ryu, S., H. Zhou, T. R. Paudel, N. Campbell, J. Podkaminer, C. W. Bark, T. Hernandez, et al. "Electronic reconstruction at the polar (111)-oriented oxide interface." APL Materials 10, no. 3 (March 1, 2022): 031115. http://dx.doi.org/10.1063/5.0067445.
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Atomically flat (111) interfaces between insulating perovskite oxides provide a landscape for new electronic phenomena. For example, the graphene-like coordination between interfacial metallic ion layer pairs can lead to topologically protected states [Xiao et al., Nat. Commun. 2, 596 (2011) and A. Rüegg and G. A. Fiete, Phys. Rev. B 84, 201103 (2011)]. The metallic ion/metal oxide bilayers that comprise the unit cell of the perovskite (111) heterostructures require the interface to be polar, generating an intrinsic polar discontinuity [Chakhalian et al., Nat. Mater. 11, 92 (2012)]. Here, we investigate epitaxial heterostructures of (111)-oriented LaAlO3/SrTiO3 (LAO/STO). We find that during heterostructure growth, the LAO overlayer eliminates the structural reconstruction of the STO (111) surface with an electronic reconstruction, which determines the properties of the resulting two-dimensional conducting gas. This is confirmed by transport measurements, direct determination of the structure and atomic charge from coherent Bragg rod analysis, and theoretical calculations of electronic and structural characteristics. Interfacial behaviors of the kind discussed here may lead to new growth control parameters useful for electronic devices.
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Turkulets, Yury, and Ilan Shalish. "(Invited) Towards GaN Passivation: Identification of GaN Surface/Interface States." ECS Meeting Abstracts MA2023-02, no. 32 (December 22, 2023): 1574. http://dx.doi.org/10.1149/ma2023-02321574mtgabs.
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GaN has been emerging as the next technological semiconductor after silicon and has already secured its superiority in the niche of power electronics with a rapidly growing interest since the advent of electric vehicles. To enable GaN to concur more microelectronic applications, one major barrier has yet to be surpassed. Rather limited control has so far been achieved over the density of GaN interface states. To achieve it, native and process-induced surface states need to be fully identified. Photoluminescence (PL) has been the most commonly used method in the study of GaN defects, and it typically shows a wide sub-bandgap peak centered at 2.2 eV that has been called the yellow luminescence (YL) band. Despite 30 years of studies, the debate as to whether this is a bulk or surface defect has not been settled. Present deep level characterization methods have not provided clear enough evidence. Theoretical studies attempted to associate this luminescence with various bulk defects, e.g., Ga-vacancies, O or O-C complexes,[1] while various optical spectroscopy studies, point to a surface origin.[2] Here, we report results of using an optical spectroscopy method based on surface photovoltage before and after a mild anneal in vacuum. The method is capable of showing the energy distribution of charge density trapped in surface states and thus of monitoring changes thereof. Using the method in air on untreated GaN reveals two peaks over the same ranges of the yellow and blue peaks observed by PL. After a mild anneal at 170 C for 24 hrs in vacuum, the “yellow” charge density peak was absent. Exposure to air was then observed to fully restore the “yellow” charge density peak. This observation clearly points to the involvement of an airborne molecule, a constituent of air, as the source for charge in the yellow-luminescence-related state. If this deep level were a bulk defect, it would not be able to interact with air. This observed interaction with air thus provides a first direct evidence that the yellow luminescence-related defect is a surface state. Experiments of controlled exposure to the various air constituents to identify the related airborne molecule are currently ongoing. The same method is now used in a search for passivation method for this surface state. The method we use is based on the following model. Illumination using sub-band gap photon energies excites electrons from the surface states over the surface potential barrier, consequently, reducing the surface band bending, and this change is observed as photovoltage (Fig. 1). We have already shown how this photovoltage can be used for calculation of the surface charge distribution in GaN HEMT.[3] In the case of bulk crystal, the model is slightly different, and a quantitative relation may be obtained between the measured photovoltage and the surface state charge distribution. Quantitative calculation requires knowledge of the surface band bending in equilibrium, which may not always be reliably obtained. However, when the spectrum is acquired using low photon flux, assuring the change in the band bending is small compared with the equilibrium band bending the surface charge density is practically relative to the derivative of the photovoltage, and thus, qualitative distribution may be obtained.[4] Figure 2 exemplifies the use of the model presented here to obtain a qualitative charge density spectrum. It shows surface charge density obtained using the model from the photovoltage spectrum shown as inset. This method is then used in Fig. 3 to compare three spectra of the same sample: In air (red), in vacuum (green) - the yellow peak is slightly reduced, and after heating up to 450 K for 24 h in vacuum (blue) - the yellow peak is practically gone. These results suggest that the charge in the yellow-luminescence-related state is contributed by a non-inert constituent of air, and this interaction may not be possible unless this state is a surface state. In the talk, preliminary results on the chemical identity of this air constituent will be presented. [1] Van de Walle et al., Microscopic origins of surface states on nitride surfaces, J. Appl. Phys. 101, 081704 (2007). [2] Shalish et al., Yellow luminescence and related deep levels in unintentionally doped GaN films, Phys. Rev. B 59, 9748 (1999). [3] Turkulets et el., Surface states in AlGaN/GaN high electron mobility transistors: Quantitative energetic profiles and dynamics of the surface Fermi level, Appl. Phys. Lett. 115, 023502 (2019). [4] Turkulets et al. The GaN(0001) yellow-luminescence-related surface state and its interaction with air. Surfaces and Interfaces 38, 102834 (2023). Figure 1
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Dusilo, Katarzyna, and Marcin Opallo. "Voltammetry in Microemulsion Formed by Electron Donor Solution in Organic Solvent|Ionic Liquid Microdroplets in Aqueous Electrolyte." ECS Meeting Abstracts MA2023-02, no. 56 (December 22, 2023): 2731. http://dx.doi.org/10.1149/ma2023-02562731mtgabs.
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Oxygen reduction reaction (ORR)1 or hydrogen evolution reaction (HER)2 at liquid|liquid interface provide the possibility of separation of their products: hydrogen peroxide or hydrogen.3,4 Typically, these reactions are studied at single interface formed between immiscible electrolyte solutions in quiescent conditions. In such geometry the frequency of successful reaction events when highly hydrophobic electron donor (i.e. decamethylferrocene (DMFc) or excited form of decamethylruthenocene (DMRc)) dissolved in organic phase meet proton from aqueous phase is rather limited. Importantly, electrochemical recycling of electron donor at electrode positioned close to the liquid|liquid interface increases efficiency of this reaction.5,6 The use of microemulsion is promising higher efficiency alternative, because of extended interfacial area of numerous organic droplets. As efficient electron exchange between oxidized form of electron donor and the electrode is crucial for biphasic ORR and HER one has to focus on electrochemical studies of DMFc or DMRc in emulsions.are important. Voltammetric signal of various redox probes as ferrocene or ferrocene surfactants in quiescent emulsions is similar to that in single phase with some variation of peak density currents or redox potential.7-11 Other studies focused on chronoamperometric experiments to detect collisions of redox probe (e.g. ferrocene12) containing droplets with the electrode surface. It was found that the addition of an hydrophobic ionic liquid, typically trihexyltetradecyl-phosphonium bis(trifluoro-methylsulfonyl) amide to the organic phase as stabiliser and electrolyte, does not influence the magnitude of the electrochemical signal.13 Here we will report results of electrochemical studies of emulsion prepared from aqueous HClO4 and DMFc or DMRc and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide (IL-PI) solution in toluene. As aqueous phase acid solution was selected, because in biphasic ORR or HER it serves as a source of protons. During the measurements the microemulsion was stirred to achieve faster droplets transport towards the electrode surface. Results will be compared with these obtained in a single organic phase. Voltammograms obtained with glassy carbon disc electrode indicate reversible oxidation/reduction of the redox probe similar to the seen with an electrode immersed in single organic phase. During continuous scanning redox only small change of peak currents is seen. Importantly, when after experiment in emulsion working electrode was transferred to aqueous HClO4, the voltammetric signal is still seen, but the peak currents are significantly smaller. This may indicate the redox reaction in liquid film formed on the electrode surface. Formation of liquid organic film is confirmed by the results of chronoamperometric experiments. When the electrode is set at potential corresponding to the oxidation of the redox probe, of the current is seen after c.a. 100 s drop, what may indicate the gradient of redox probe concentration. As DMFc is insoluble in water this points out on gradient of organic phase close to the glassy carbon surface.14 In turn voltammetric current related to electroreduction of highly hydrophilic hexacyanoferrate(III) is significantly diminished in emulsion as compared to pure aqueous electrolyte indicating partial coverage of the GC surface by hydrophobic film. Other effects related with electrochemical behavior of studied emulsions will be also presented and discussed. References: Su et al., Angew. Chem. Int. Ed., 120, 4753 (2008). Hatay et al., Angew. Chemie Int. Ed., 121, 5241 (2009). Opallo et al., ChemElectroChem, 9, e202200513 (2022). Gamero-Quijano et al., Curr. Op. Electrochem., 38, 101212 (2023). Jedraszko et al., Chem. Commun., 51, 6851 (2015). Jedraszko et al., J. Electroanal. Chem., 819, 101 (2018). Gounili et al., Langmuir, 11, 2800 (1995). M. Shah et al., Langmuir, 13, 4729 (1997). F. Rusling et al., J. Electroanal. Chem., 437, 97 (1997). Peng et al., ACS App. Mater. Interfaces, 12, 40213 (2020). Peng et al., Electrochim. Acta., 393, 139048, (2021). Li et al., Anal. Chem. , 87, 23 (2015). K. Kim et al., J. Am. Chem. Soc., 136, 13 (2014). T. Tichter et al. ChemElectroChem, 8, 3397 (2021).
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Ishimi, Shota, Makoto Hirose, Yasuo Shimizu, Yutaka Ohno, Yasuyoshi Nagai, Jianbo Liang, and Naoteru Shigekawa. "Fabrication and Electrical Characterization of GaAs/GaN Junctions." ECS Meeting Abstracts MA2023-02, no. 33 (December 22, 2023): 1598. http://dx.doi.org/10.1149/ma2023-02331598mtgabs.
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GaAs/GaN heterojunctions are likely to be an ideal platform for high-frequency/high-output-power electron devices because of excellent electrical properties of GaAs and GaN as well as the similarity in their coefficients of thermal expansion. We have to note, however, that heteroepitaxial growth of GaAs/GaN junctions is quite difficult because of difference in crystal structures (in case of GaAs/wurtzite GaN junctions) and large mismatch in lattice constants (GaAs/zincblende GaN junctions). In this work we fabricate p+-GaAs/n-GaN heterojunctions by bonding GaAs and GaN epi wafers to each other using surface-activated-bonding technologies [1,2], selectively etching off the GaAs substrate used in the epitaxial growth, making ohmic contacts on the exposed surface of GaAs layer, and forming GaAs mesas. Ohmic contacts on the backside of GaN epi wafer are formed before bonding. The junctions are annealed at 400 ℃ in contact formation on GaAs surfaces. The temperature is much lower in comparison with the temperature in a wafer-fusion process of GaAs and GaN (750 ℃), which were reportedly applied for fabricating group-III arsenide/nitride heterojunction bipolar transistors [3]. Observation using cross sectional transmission electron microscope (TEM) of as-bonded and 400-℃ annealed GaAs/GaN interfaces shows that no voids are formed at the GaN/GaAs interfaces by the 400-℃ annealing. We also fabricate n+-GaAs/n-GaN heterojunctions for comparison. We measure the capacitance-voltage characteristics and current-voltage characteristics for reverse-bias voltages of the p+-GaAs/n-GaN and n+-GaAs/n-GaN junctions and find that the characteristics of the two junctions are close to each other, which suggests that the band profiles of GaN layers in the p+-GaAs/n-GaN and n+-GaAs/n-GaN junctions are almost the same, i.e., the Fermi-level pinning occurs at the GaAs/GaN interfaces. More importantly, the reverse-bias characteristics are measured up to -60 V. The reverse-bias voltage corresponds to an electric field of as high as ~2 MV/cm, which is comparable to the breakdown field of GaN (3-4 MV/cm) [4]. We also excite minority electrons in the p+-GaAs layer using a 488-nm Ar laser and successfully observe the photo current due to the transport of minority electrons across the reverse-biased GaAs/GaN interfaces. Acknowledgement: TEM samples were fabricated under the Inter-University Cooperative Research in IMR of Tohoku University. Epi wafers used in the work were provided from Sciocs (present Sumitomo Chemical) Co., Ltd. [1] H. Takagi, et al. Appl. Phys. Lett. 68, 2222 (1996). [2] S. Yamajo, et al., Jpn. J. Appl. Phys. 57, 02BE02 (2018). [3] C. Lian, et al. Appl. Phys. Lett. 91, 063502 (2007). [4] T. Maeda, et al., IEEE Electron Device Lett., 43, 96 (2022).
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Aubert, M. "La méthode de polarisation spontanée en hydrogéologie des terrains volcaniques." Revue des sciences de l'eau 16, no. 2 (April 12, 2005): 219–35. http://dx.doi.org/10.7202/705505ar.
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En terrain volcanique, les eaux de pluie s'infiltrent jusqu'à leur rencontre avec un niveau imperméable qui correspond le plus souvent au socle cristallin. Ce sont les talwegs et les lignes de crête des paléo- reliefs de ce socle dont la profondeur peut dépasser la centaine de mètres qu'il convient de détecter, parfois avec une précision décamétrique. La méthode géophysique la plus utilisée en hydrogéologie des terrains volcaniques est la prospection électrique qui fournit des coupes verticales des résistivités électriques. La morphologie du substratum imperméable ou saturé peut aussi être obtenue en mesurant en surface les potentiels électriques de polarisation spontanée (en abrégé PS) qui se forment par la percolation de l'eau infiltrée dans le terrain poreux. La base de la zone non saturée, appelée surface SPS, est calculée par une relation faisant intervenir les données PS, les altitudes et deux coefficients définis à partir des données géologiques. Cette surface indique directement les axes de circulation et les lignes de partage des eaux. Deux exemples pris sur des sites bien documentés montrent la validité de la méthode pour localiser les axes de circulation de l'eau souterraine et les limites entre bassins versants. Un troisième exemple montre les résultats PS comparés à ceux des méthodes électromagnétiques VLF et AMT. La méthode PS est légère et offre une bonne précision horizontale, mais elle demande au moins un forage d'étalonnage pour préciser la profondeur des interfaces.