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Huma, Tabasum, Nadimullah Hakimi, Muhammad Younis, Tanzeel Huma, Zhenhua Ge, and Jing Feng. "MgO Heterostructures: From Synthesis to Applications." Nanomaterials 12, no. 15 (August 3, 2022): 2668. http://dx.doi.org/10.3390/nano12152668.
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The energy storage capacity of batteries and supercapacitors has seen rising demand and problems as large-scale energy storage systems and electric gadgets have become more widely adopted. With the development of nano-scale materials, the electrodes of these devices have changed dramatically. Heterostructure materials have gained increased interest as next-generation materials due to their unique interfaces, resilient structures and synergistic effects, providing the capacity to improve energy/power outputs and battery longevity. This review focuses on the role of MgO in heterostructured magnetic and energy storage devices and their applications and synthetic strategies. The role of metal oxides in manufacturing heterostructures has received much attention, especially MgO. Heterostructures have stronger interactions between tightly packed interfaces and perform better than single structures. Due to their typical physical and chemical properties, MgO heterostructures have made a breakthrough in energy storage. In perpendicularly magnetized heterostructures, the MgO’s thickness significantly affects the magnetic properties, which is good news for the next generation of high-speed magnetic storage devices.
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Slepchenkov, Michael M., Dmitry A. Kolosov, Igor S. Nefedov, and Olga E. Glukhova. "Band Gap Opening in Borophene/GaN and Borophene/ZnO Van der Waals Heterostructures Using Axial Deformation: First-Principles Study." Materials 15, no. 24 (December 13, 2022): 8921. http://dx.doi.org/10.3390/ma15248921.
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One of the topical problems of materials science is the production of van der Waals heterostructures with the desired properties. Borophene is considered to be among the promising 2D materials for the design of van der Waals heterostructures and their application in electronic nanodevices. In this paper, we considered new atomic configurations of van der Waals heterostructures for a potential application in nano- and optoelectronics: (1) a configuration based on buckled triangular borophene and gallium nitride (GaN) 2D monolayers; and (2) a configuration based on buckled triangular borophene and zinc oxide (ZnO) 2D monolayers. The influence of mechanical deformations on the electronic structure of borophene/GaN and borophene/ZnO van der Waals heterostructures are studied using the first-principles calculations based on density functional theory (DFT) within a double zeta plus polarization (DZP) basis set. Four types of deformation are considered: uniaxial (along the Y axis)/biaxial (along the X and Y axes) stretching and uniaxial (along the Y axis)/biaxial (along the X and Y axes) compression. The main objective of this study is to identify the most effective types of deformation from the standpoint of tuning the electronic properties of the material, namely the possibility of opening the energy gap in the band structure. For each case of deformation, the band structure and density of the electronic states (DOS) are calculated. It is found that the borophene/GaN heterostructure is more sensitive to axial compression while the borophene/ZnO heterostructure is more sensitive to axial stretching. The energy gap appears in the band structure of borophene/GaN heterostructure at uniaxial compression by 14% (gap size of 0.028 eV) and at biaxial compression by 4% (gap size of 0.018 eV). The energy gap appears in the band structure of a borophene/ZnO heterostructure at uniaxial stretching by 10% (gap size 0.063 eV) and at biaxial compression by 6% (0.012 eV). It is predicted that similar heterostructures with an emerging energy gap can be used for various nano- and optoelectronic applications, including Schottky barrier photodetectors.
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Yin, Yunzhen, Yanyan Bu, and Xiangfu Wang. "Simulation of light transmission through core-shell heterostructure nano-materials." Chemical Physics 535 (July 2020): 110785. http://dx.doi.org/10.1016/j.chemphys.2020.110785.
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Fu, Nanxin, Jiazhen Zhang, Yuan He, Xuyang Lv, Shuguang Guo, Xingjun Wang, Bin Zhao, Gang Chen, and Lin Wang. "High-Sensitivity 2D MoS2/1D MWCNT Hybrid Dimensional Heterostructure Photodetector." Sensors 23, no. 6 (March 14, 2023): 3104. http://dx.doi.org/10.3390/s23063104.
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A photodetector based on a hybrid dimensional heterostructure of laterally aligned multiwall carbon nanotubes (MWCNTs) and multilayered MoS2 was prepared using the micro-nano fixed-point transfer technique. Thanks to the high mobility of carbon nanotubes and the efficient interband absorption of MoS2, broadband detection from visible to near-infrared (520–1060 nm) was achieved. The test results demonstrate that the MWCNT-MoS2 heterostructure-based photodetector device exhibits an exceptional responsivity, detectivity, and external quantum efficiency. Specifically, the device demonstrated a responsivity of 3.67 × 103 A/W (λ = 520 nm, Vds = 1 V) and 718 A/W (λ = 1060 nm, Vds = 1 V). Moreover, the detectivity (D*) of the device was found to be 1.2 × 1010 Jones (λ = 520 nm) and 1.5 × 109 Jones (λ = 1060 nm), respectively. The device also demonstrated external quantum efficiency (EQE) values of approximately 8.77 × 105% (λ = 520 nm) and 8.41 × 104% (λ = 1060 nm). This work achieves visible and infrared detection based on mixed-dimensional heterostructures and provides a new option for optoelectronic devices based on low-dimensional materials.
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Ren, Lingling, and Baojuan Dong. "Ferroelectric Polarization in an h-BN-Encapsulated 30°-Twisted Bilayer–Graphene Heterostructure." Magnetochemistry 9, no. 5 (April 26, 2023): 116. http://dx.doi.org/10.3390/magnetochemistry9050116.
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Recently, the emergent two-dimensional (2D) ferroelectric materials have provided new possibilities for the miniaturization of ferroelectric systems and the integration of novel 2D nano-electronic devices. In addition to the intrinsic ferroelectrics exfoliated from bulk, 2D heterostructures hybridized from electrically non-polarized van der Waals (vdW) materials have also been proven to be a promising platform for the construction of ferroelectricity. Here, we report 30° twisted bilayer–graphene (TBLG) incommensurate moiré superlattice encapsulated by hexagonal boron nitride (h-BN), in which robust hysteretic resistance was detected at the top interface between h-BN and the TBLG from room temperature down to 40 mK. The hysteretic phenomenon can be understood by the extra carrier induced by the interfacial 2D ferroelectric polarization, which is estimated to be around 0.7 pC/m. Our work of interfacial ferroelectric heterostructure achieved by a TBLG/h-BN hybrid system expands the 2D ferroelectric families and opens more possibilities for future coupling the ferroelectricity with rich electronic and optical properties in vdW twistronic devices.
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Wang, Qianqian, Yujie Ma, Li Liu, Shuyue Yao, Wenjie Wu, Zhongyue Wang, Peng Lv, et al. "Plasma Enabled Fe2O3/Fe3O4 Nano-aggregates Anchored on Nitrogen-doped Graphene as Anode for Sodium-Ion Batteries." Nanomaterials 10, no. 4 (April 18, 2020): 782. http://dx.doi.org/10.3390/nano10040782.
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Low electrical conductivity severely limits the application of Fe2O3 in lithium- and sodium-ion batteries. In respect of this, we design and fabricate Fe2O3/Fe3O4 nano-aggregates anchored on nitrogen-doped graphene as an anode for sodium-ion batteries with the assistance of microwave plasma. The highly conductive Fe3O4 in the composite can function as a highway of electron transport, and the voids and phase boundaries in the Fe2O3/Fe3O4 heterostructure facilitate Na+ ion diffusion into the nano-aggregates. Furthermore, the Fe–O–C bonds between the nano-aggregates and graphene not only stabilize the structural integrity, but also enhance the charge transfer. Consequently, the Fe2O3/Fe3O4/NG anode exhibits specific capacity up to 362 mAh g−1 at 100 mA g−1, excellent rate capability, and stable long-term cycling performance. This multi-component-based heterostructure design can be used in anode materials for lithium- and sodium-ion batteries, and potential opens a new path for energy storage electrodes.
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Shukla, Ayushi, and Pooja Srivastava. "Van der Waals Heterostructures for device Applications." SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 13, no. 01 (June 30, 2021): 48–52. http://dx.doi.org/10.18090/samriddhi.v13i01.9.
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Advent of two-dimensional (2D) materials owing to their extraordinary properties can revolutionize the field of nano-electronics. Experimental advancements have now made it possible to stack different 2D layers on top of each other to form a single system. Due to van der Waals bonding between the layers, the properties of each layer are not perturbed much. It helps in generating new functionalities for nano-electronics applications. The present paper focuses on the application of van der Waals heterostructure.
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Sun, Ying-Hui, Cong-Yan Mu, Wen-Gui Jiang, Liang Zhou, and Rong-Ming Wang. "Interface modulation and physical properties of heterostructure of metal nanoparticles and two-dimensional materials." Acta Physica Sinica 71, no. 6 (2022): 066801. http://dx.doi.org/10.7498/aps.71.20211902.
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<sec>Two-dimensional (2D) material has atomic smooth surface, nano-scale thickness and ultra-high specific surface area, which is an important platform for studying the interface interaction between metal nanoparticles (NPs) and 2D materials, and also for observing the surface atomic migration, structural evolution and aggregation of metal NPs in real time and <i>in situ</i>. By rationally designing and constructing the interfaces of metal NPs and 2D materials, the characterization of the interface structure on an atomic scale is very important in revealing the structure-property relationship. It is expected that the investigation is helpful in understanding the mechanism of interaction between metal and 2D materials and optimizing the performance of the devices based on metal-2D material heterojunctions.</sec><sec>In this review, the recent progress of interface modulation and physical properties of the heterostructure of metal NPs and 2D materials are summarized. The nucleation, growth, structural evolution and characterization of metal NPs on the surface of 2D materials are reviewed. The effects of metal NPs on the crystal structure, electronic state and energy band of 2D materials are analyzed. The possible interfacial strain and interfacial reaction are also included. Because of the modulation of electrical and optical properties of 2D materials, the performance of metal NPs-2D material based field effect transistor devices and optoelectronic devices are improved. This review is helpful in clarifying the physical mechanism of microstructure affecting the properties of metal NPs-2D material heterostructures on an atomic scale, and also in developing the metal-2D material heterostructures and their applications in the fields of electronic devices, photoelectric devices, energy devices, etc.</sec>
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Rotkin, Slava V., and Tetyana Ignatova. "(Invited) Multiplexed Label-Free Biosensing Using 2D-Heterostructures: Materials Stability and Signal Uniformity." ECS Meeting Abstracts MA2022-01, no. 8 (July 7, 2022): 692. http://dx.doi.org/10.1149/ma2022-018692mtgabs.
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Two-dimensional materials (2DM) has been already applied for bio- and chemical sensing[1],[2]. Even individual 2D materials often outperform bulk analogues, showing strong response and being compatible with flexible technologies, thus opening horizons for wearable and Point-of-Care applications[3]. Most recently, emergent need to achieve better, more precise and sensitive drug detection in medicine and health care has been addressed by developing new types of biosensors[4]. Extending properties of individual 2DMs by constructing their van der Waals heterostructures, either lateral or vertical, offers new response and/or transduction mechanisms and further improvement of device performance. Such heterostructures have potential for label-free biosensing and could be designed and/or integrated together to generate several signals in response to a single analyte. Such a capability enables a multimodal detection, which exceeds single-mode biosensing through its higher throughput, as well as by better ability to differentiate the analyte from background signals in a complex media, and potentially allows multiplexing (responding by several channels to a group of substances in parallel). Despite significant efforts were invested into discovery of newer and better 2D materials with biosensing capabilities, there is only limited knowledge of factors that could limit its performance. Indeed, atomically thin 2D materials have an ultimate surface-to-volume ratio which helps sensing, but may result in surface non-uniformities at the nanometer scale such as: atomic impurities, adsorbates, single atom and lattice defects, wrinkles and ruptures – to name just a few. Such defects may modulate their sensing properties. Here, a new multidimensional optical imaging technique will be presented which is capable to detect lattice mismatch and work function difference in the heterostructure material. Those result in strain and charge transfer and vary optical response at the nanometer scale, hard to detect and study by normal characterization tools. We present a vertical heterostructure comprised of monolayer graphene and single layer flakes of MoS2. An optical label-free detection of doxorubicin, a common cancer drug, is reported via three independent optical detection channels (photoluminescence shift, Raman shift and Graphene Enhanced Raman Scattering). Non-uniform broadening of components of multimodal signal correlates with the statistical distribution of local optical properties of the 2DM heterostructure. It will be shown how mapping of distribution for doping and strain (taken with sub-diffractional resolution) allows one to understand the role of those for modulation of electronic properties of 2D material. Acknowledgement: partial support is acknowledged from NSF CHE-2032582, CHE-2032601, DMR-1539916 and DMR-2011839 grants. [1] Oh, S.-H.; et.al, Nature Communications 2021, 12, 3824. [2] Bolotsky, A.; et.al, ACS Nano 2019, 13, 9781. [3] Pang, Y.; et.al, Small 2020, 16, 1901124. [4] Moradi, R; Small (2021). doi: 10.1002/smll.202104847
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Jariwala, Deep. "(Invited) 2D Dimensional Quantum Materials for CMOS and Beyond CMOS Devices." ECS Meeting Abstracts MA2022-01, no. 29 (July 7, 2022): 1292. http://dx.doi.org/10.1149/ma2022-01291292mtgabs.
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The isolation of a growing number of two-dimensional (2D) materials has inspired worldwide efforts to integrate distinct 2D materials into van der Waals (vdW) heterostructures. While a tremendous amount of research activity has occurred in assembling disparate 2D materials into “all-2D” van der Waals heterostructures and making outstanding progress on fundamental studies, practical applications of 2D materials will require a broader integration strategy. I will present our ongoing and recent work on integration of 2D materials with 3D electronic materials to realize logic switches and memory devices with novel functionality that can potentially augment the performance and functionality of Silicon technology. First, I will present our recent work on gate-tunable diode1 and tunnel junction devices2 based on integration of 2D chalcogenides with Si and GaN. Following this I will present our recent work on non-volatile memories based on Ferroelectric Field Effect Transistors (FE-FETs) made using a heterostructure of MoS2/AlScN3 and I also will present our work on Ferroelectric Diode (ferrodiode) devices4 also based on thin AlScN. If time permits, I will also cover our ongoing efforts in scaling FE-FETs based on MoS2 and AlScN to < 100 nm channel lengths over large areas and also discuss in-memory computing using ferrodiode devices and also touch upon our efforts in photonics and light trapping using 2D semiconductors. I will end by giving a broad perspective on future opportunities of 2D semiconductors in micro and nanoelectronics. References: Miao, J.; Liu, X.; Jo, K.; He, K.; Saxena, R.; Song, B.; Zhang, H.; He, J.; Han, M.-G.; Hu, W.; Jariwala, D. Nano Letters 2020, 20, (4), 2907-2915. Miao, J.; Leblanc, C.; Liu, X.; Song, B.; Zhang, H.; Krylyuk, S.; Davydov, A. V.; Back, T.; Glavin, N. R.; Jariwala, D.,2D Metal Selenide-Silicon Steep Sub-Threshold Heterojunction Triodes with High On-Current Density arXiv:2111.06396 Liu, X.; Wang, D.; Zheng, J.; Musavigharavi, P.; Miao, J.; Stach, E. A.; Olsson III, R. H.; Jariwala, D. Nano Letters 2021, 21, 3753–3761. Liu, X.; Zheng, J.; Wang, D.; Musavigharavi, P.; Stach, E. A.; Olsson III, R.; Jariwala, D. Applied Physics Letters 2021, 118, 202901
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Hamlin, Andrew Bradford, Youxiong Ye, Julia Elizabeth Huddy, and William Joseph Scheideler. "Modulation Doped 2D InOx/GaOx Heterostructure Tfts Via Liquid Metal Printing." ECS Meeting Abstracts MA2022-01, no. 31 (July 7, 2022): 1326. http://dx.doi.org/10.1149/ma2022-01311326mtgabs.
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Indium gallium zinc oxide (IGZO) and similar wide bandgap metal oxides are among the most widely used channel materials for drive transistors in displays due to their excellent electronic mobility and their ultra-high transparency1. However, industry-standard processing involves expensive vacuum deposition and elevated activation temperatures to produce semiconducting thin films. Liquid metal printing (LMP) is an emerging technique for oxide semiconductor fabrication poised to overcome these drawbacks via scalable vacuum-free transfer of the native oxide layers formed by spontaneous surface oxidation of molten metals2–4. Heterostructures of these 1-4 nm 2D oxide layers provide unprecedented opportunities for engineering electrostatic control of multilayers in thin film transistors, leading to improved mobility, Ion/Ioff ratios, and faster switching capabilities. Likewise, the backchannel is of high importance to these devices, as selection of an appropriate capping layer can enhance performance via remote doping while also mitigating bias stress effects. Herein, we compare the results of heterostructure InOx/GaOx with pure InOx TFTs, which demonstrates the mobility enhancement provided by GaOx modulation doping. Bottom gate thin film transistors (TFTs) (Figures 1a and 1b) were fabricated on Si substrates with 100 nm of thermally grown SiO2. 4 nm thick InOx and GaOx were deposited at 240 ˚C and 180 ˚C, respectively, using a linear printing speed of 8 cm/s. InOx and GaOx were printed in less than 10 s, with no post annealing necessary. Figure 1c illustrates the proposed mechanism for electron donation from GaOx at the heterointerface with InOx. The conduction band offset between these materials results in band bending at the interface and an increased carrier concentration in the InOx layer. The substoichiometric, defective GaOx is expected to further enhance this effect. Figure 1d demonstrates the transfer characteristics of heterostructure InOx/GaOx in comparison with pure InOx. The improved mobility for the heterostructure (7.8 cm2/Vs) vs pure InOx (3.8 cm2/Vs) channels can be attributed to modulation doping provided by GaOx and can be analyzed by extracting the electronic density of states (eDOS). These results illustrate a unique capability of LMP, which is to engineer the electronic structure of highly conductive 2D oxides while maintaining electrostatic control. This work also investigates the material properties of these 2D oxide heterostructures by UV-vis, XRD and XPS characterization. UV-Vis analysis revealed that the GaOx capping layer induces band gap widening and enhanced transparency, which can be explained by the Burstein-Moss effect from modulation doping. Unique to this LMP process is also the low temperature crystallization of the InOx films. XRD showed that even with low deposition temperatures (200 – 240 ˚C), these InOx films are highly crystalline with grain sizes substantially larger than the film thickness. Finally, XPS analysis of the O1s peak was utilized to understand the stoichiometry and interactions between the InOx and GaOx layers. This work demonstrates an effective pathway to enhance electronic transport in semiconducting metal oxides through liquid metal printed 2D heterostructures. The ultrathin films produced by LMP are well suited for thin film devices requiring nm-scale electrostatic control for effective gating. Combining this 2D nature of LMP InOx with a 2D GaOx backchannel capping layer is shown to yield high-performance printed transistors. This approach demonstrates a rapid, open-air compatible and low temperature manufacturing method, elucidating the broad impact of this technology in display fabrication, low-cost and flexible electronics. H. Hosono, Nat Electron, 1, 428–428 (2018). K. A. Messalea et al., ACS Nano, 15, 16067–16075 (2021). R. S. Datta et al., Nat Electron, 3, 51–58 (2020). A. Jannat et al., ACS Nano, 15, 4045–4053 (2021). A. Goff et al., Dalton Transactions, 50, 7513–7526 (2021). C.-H. Choi, Y.-W. Su, L.-Y. Lin, C.-C. Cheng, and C. Chang, RSC Advances, 5, 93779–93785 (2015). Figure 1
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Lee, Kwang Se, Jung Yong Kim, Jongwook Park, Jang Myoun Ko, and Sharon Mugobera. "Two-Dimensional Heterostructure of PPy/CNT–E. coli for High-Performance Supercapacitor Electrodes." Materials 15, no. 17 (August 23, 2022): 5804. http://dx.doi.org/10.3390/ma15175804.
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The nano-biocomposite electrodes composed of carbon nanotube (CNT), polypyrrole (PPy), and E. coli-bacteria were investigated for electrochemical supercapacitors. For this purpose, PPy/CNT–E. coli was successfully synthesized through oxidative polymerization. The PPy/CNT–E. coli electrode exhibited a high specific capacitance of 173 F∙g−1 at the current density of 0.2 A∙g−1, which is much higher than that (37 F∙g−1) of CNT. Furthermore, it displayed sufficient stability after 1000 charge/discharge cycles. The CNT, PPy/CNT, and PPy/CNT–E. coli composites were characterized by x-ray diffraction, scanning electron microscopy, and surface analyzer (Brunauer–Emmett–Teller, BET). In particular, the pyrrole monomers were easily adsorbed and polymerized on the surface of CNT materials, as well as E. coli bacteria enhanced the surface area and porous structure of the PPy/CNT–E. coli composite electrode resulting in high performance of devices.
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Jebali, Sana, Mahdi Meftah, Chadha Mejri, Abdesslem Ben Haj Amara, and Walid Oueslati. "Enhancement of Photocatalytic Activity and Microstructural Growth of Cobalt-Substituted Ba1−xCoxTiO3 {x = 0, …, 1} Heterostructure." ChemEngineering 7, no. 3 (May 1, 2023): 43. http://dx.doi.org/10.3390/chemengineering7030043.
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The photocatalytic degradation process and absorption kinetics of the aqueous solution of the Cibacron Brilliant Yellow 3G-P dye (Y) were investigated under UV-Vis light. Pure barium titanate BaTiO3 (BT) and cobalt ion-substituted barium Ba1−xCoxTiO3 (x = 0, …, 1) nano-compound powders (BCT) were synthesized using the sol–gel method and colloidal solution destabilization, and utilized as photocatalysts. The powder X-ray diffraction (PXRD) crystal structure analysis of the BT nanoparticles (NPs) revealed a prominent reflection corresponding to the perovskite structure. However, impurities and secondary phase distributions were qualitatively identified in the PXRD patterns for x ≥ 0.2 of cobalt substitution rate. Rietveld refinements of the PXRD data showed that the BCT nano-compound series undergoes a transition from perovskite structure to isomorphous ilmenite-type rhombohedral CoTiO3 (CT) ceramic. The nanoparticles produced displayed robust chemical interactions, according to a Fourier transform infrared spectroscopy (FTIR) analysis. The BT and BCT nanoparticles had secondary hexagonal phases that matched the PXRD results and small aggregated, more spherically shaped particles with sizes ranging from 30 to 114 nm, according to transmission electron microscopy (TEM). Following a thorough evaluation of BCT nano-compounds with (x = 0.6), energy-dispersive X-ray (EDX) compositional elemental analysis revealed random distributions of cobalt ions. Through optical analysis of the photoluminescence spectra (PL), the electronic structure, charge carriers, defects, and energy transfer mechanisms of the compounds were examined. Due to the cobalt ions being present in the BT lattice, the UV-visible absorption spectra of BCT showed a little red-shift in the absorption curves when compared to pure BT samples. The electrical and optical characteristics of materials, such as their photon absorption coefficient, can be gathered from their UV-visible spectra. The photocatalytic reaction is brought about by the electron–hole pairs produced by this absorption. The estimated band gap energies of the examined compounds, which are in the range of 3.79 to 2.89 eV, are intriguing and require more investigation into their potential as UV photocatalysts. These nano-ceramics might be able to handle issues with pollution and impurities, such as the breakdown of organic contaminants and the production of hydrogen from water.
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Hossain, Ridwan F., Misook Min, and Anupama B. Kaul. "High-Performance, Flexible, Inkjet Printed Heterostructure Photodetector for Biosensing Applications." MRS Advances 4, no. 10 (2019): 621–27. http://dx.doi.org/10.1557/adv.2019.69.
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ABSTRACTAge-related macular degeneration (AMD), a retinal degenerative disease that results in a continuous degeneration of photoreceptors in the retina, which eventually leads to complete blindness. One approach to combat AMD is through the use of artificially implantable photodetectors that are physically placed on the retina. Interestingly, 2D materials such as photosensitive and semiconducting molybdenum disulfide (MoS2) and electrically conducting graphene have recently received tremendous promise due to their unique photonic and optoelectronic properties and their potential in various types of micro and nano-devices. In this study, a highly biocompatible 2D graphene-MoS2 photodetectors on a flexible polyimide substrate were designed, fabricated using inkjet printing to form photosensitive pixels and tested as a function of photo intensity and strain. The inkjet printed 2D heterostructure devices were photoresponsive and the photocurrent scaled proportionally with the incident light intensity, exhibiting a photoresponsivity R ∼ 0.30 A/W at room temperature. The strain-dependent measurements of photocurrent with bending showed a photocurrent of Iph ∼ 1.16 μA with strain levels for curvature up to ∼ 0.262 cm-1. Inkjet printed graphene and MoS2 inks were also characterized using techniques such as Raman Spectroscopy, Photoluminescence (PL) and Scanning Electron Microscopy (SEM).
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Hao, Guo-Qiang, Rui Zhang, Wen-Jing Zhang, Na Chen, Xiao-Jun Ye, and Hong-Bo Li. "Regulation and control of Schottky barrier in graphene/MoSe<sub>2</sub> heteojuinction by asymmetric oxygen doping." Acta Physica Sinica 71, no. 1 (2022): 017104. http://dx.doi.org/10.7498/aps.71.20210238.
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Although graphene-based heterostructures exhibit excellent intrinsic properties for device scaling, fabricating low Schottky barrier is still a great challenge to the electrical transport behaviors of nanoelectronic devices. Exploring excellent materials for electronic devices are a research hotspot at present. Graphene not only exhibits excellent physical strength and specific surface area, but also presents high carrier mobility and thermal conductivity. Therefore, graphene has been developed in many fields such as energy, catalysis, etc. However, graphene is a special material with zero band gap, and its electrons and holes are easy to compound, which seriously hinders its development in the applications of electronic and optoelectronic devices. Two-dimensional transition metal dichalcogenides (TMDs) have the advantages of controllable band gap properties, which makes them have a good development in logic circuits and photodetectors. As one of TMD<sub>S</sub>, MoSe<sub>2</sub> possesses the advantages of narrower band gap, better electron hole separation and stronger oxidation resistance in the environment. Therefore, the design of graphene and MoSe<sub>2</sub> heterostructures is an ideal choice for a new generation of nanoelectronic devices. Here, we investigate systematically the effects of asymmetric O doping on the electronic properties and Schottky barrier of graphene/MoSe<sub>2(1–<i>x</i>)</sub>O<sub>2<i>x</i></sub> heterostructure for the first time by first-principles calculations incorporating semiempirical dispersion-correction scheme. The results indicate that graphene and MoSe<sub>2</sub> monolayer can form a stable van der Waals heterostructure with preserving their own intrinsic properties. In addition, an n-type schottky contact with a barrier height of 0.558 eV is obtained. Further, it is found that the type and the height of the Schottky barrier can be controlled by changing the concentration and sites of the O dopant at interface. By increasing the concentration of the O dopant inside the interface, the transition from an n-type Schottky contact to an Ohmic contact can be realized, and a low n-type Schottky barrier is gained with increasing the concentration of the O dopant outside the interface for highly efficient charge transfer. The barrier height of heterostructure decreases from 0.558 eV to 0.112 eV when the O dopant is doped on the outer interface. Finally, as a complement to previous results, it is confirmed that the redistribution of interfacial charges leads the Fermi level to shift, and thus determining the type and the height of Schottky barrier. This study may provide theoretical guidance for designing and manufacturing the MoSe<sub>2</sub>-based nano field effect transistors.
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Zhang, Ke, Yang Wei, Jin Zhang, He Ma, Xinhe Yang, Gaotian Lu, Kenan Zhang, Qunqing Li, Kaili Jiang, and Shoushan Fan. "Electrical control of spatial resolution in mixed-dimensional heterostructured photodetectors." Proceedings of the National Academy of Sciences 116, no. 14 (March 19, 2019): 6586–93. http://dx.doi.org/10.1073/pnas.1817229116.
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Low-dimensional nanomaterials, such as one-dimensional (1D) nanomaterials and layered 2D materials, have exhibited significance for their respective unique electronic and optoelectronic properties. Here we show that a mixed-dimensional heterostructure with building blocks from multiple dimensions will present a synergistic effect on photodetection. A carbon nanotube (CNT)–WSe2–graphene photodetector is representative on this issue. Its spatial resolution can be electrically switched between high-resolution mode (HRM) and low-resolution mode (LRM) revealed by scanning photocurrent microscopy (SPCM). The reconfigurable spatial resolution can be attributed to the asymmetric geometry and the gate-tunable Fermi levels of these low-dimensional materials. Significantly, an interference fringe with 334 nm in period was successfully discriminated by the device working at HRM, confirming the efficient electrical control. Electrical control of spatial resolution in CNT–WSe2–graphene devices reveals the potential of the mixed-dimensional architectures in future nanoelectronics and nano-optoelectronics.
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Pokutnyi, S. I., and N. G. Shkoda. "Electron tunneling in the germanium/silicon heterostructure with germanium quantum dots: theory." Himia, Fizika ta Tehnologia Poverhni 12, no. 4 (December 30, 2021): 306–13. http://dx.doi.org/10.15407/hftp12.04.306.
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It is shown that electron tunneling through a potential barrier that separates two quantum dots of germanium leads to the splitting of electron states localized over spherical interfaces (a quantum dot – a silicon matrix). The dependence of the splitting values of the electron levels on the parameters of the nanosystem (the radius a quantum dot germanium, as well as the distance D between the surfaces of the quantum dots) is obtained. It has been shown that the splitting of electron levels in the QD chain of germanium causes the appearance of a zone of localized electron states, which is located in the bandgap of silicon matrix. It has been found that the motion of a charge-transport exciton along a chain of quantum dots of germanium causes an increase in photoconductivity in the nanosystem. It is shown that in the QD chain of germanium a zone of localized electron states arises, which is located in the bandgap of the silicon matrix. Such a zone of local electron states is caused by the splitting of electron levels in the QD chain of germanium. Moreover, the motion of an electron in the zone of localized electron states causes an increase in photoconductivity in the nanosystem. The effect of increasing photoconductivity can make a significant contribution in the process of converting the energy of the optical range in photosynthesizing nanosystems. It has been found that comparison of the splitting dependence of the exciton level Eех(а) at a certain radius a QD with the experimental value of the width of the zone of localized electron states arising in the QD chain of germanium, allows us to obtain the distances D between the QD surfaces. It has been shown that by changing the parameters of Ge/Si heterostructures with germanium QDs (radius of a germanium QD, as well as the distance D between the surfaces of the QDs), it is possible to vary the positions and widths of the zones of localized electronic states. The latter circumstance opens up new possibilities in the use of such nanoheterostructures as new structural materials for the creation of new nano-optoelectronics and nano-photosynthesizing devices of the infrared range.
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Chen, Jia-Le, Jing-Xue Du, Jing Yang, and Li-Jie Shi. "Modulation of strain on electronic structure and contact type of BP/SnS van der waals heterostructure." Journal of Physics D: Applied Physics 55, no. 12 (December 24, 2021): 125102. http://dx.doi.org/10.1088/1361-6463/ac4368.
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Abstract Vertical van der Waals heterostructures (vdWH) composed of two monolayer (ML) materials can provide new opportunities for layered electronic devices. Here we present a detailed theoretical investigation about the electronic properties of BP/SnS vdWH by applying in-plane uniaxial and biaxial strains. Our first principles calculations suggest that the direct bandgap of BP/SnS vdWH can be maintained within a large range of uniaxial and biaxial strains. We also find that the bandgap, band alignment and contact type of BP/SnS vdWH can be tuned by uniaxial and biaxial strains. In addition, the Poisson’s ratio exhibits an intense anisotropy with respect to the uniaxial strain along zigzag (ZZ) and armchair directions. The easily tunable electronic properties and highly anisotropic character of BP/SnS vdWH make it to be a promising material in the field of photovoltaic cells, photodetectors, and other functional nano devices.
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Wan, Caichao, Yue Jiao, Daxin Liang, Yiqiang Wu, and Jian Li. "Nature-Inspired Materials: A Geologic Architecture System-Inspired Micro-/Nano-Heterostructure Design for High-Performance Energy Storage (Adv. Energy Mater. 33/2018)." Advanced Energy Materials 8, no. 33 (November 2018): 1870145. http://dx.doi.org/10.1002/aenm.201870145.
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Liang, Shuting, Chaowei Wang, Fengjiao Li, and Gang Song. "Supported Cu/W/Mo/Ni—Liquid Metal Catalyst with Core-Shell Structure for Photocatalytic Degradation." Catalysts 11, no. 11 (November 22, 2021): 1419. http://dx.doi.org/10.3390/catal11111419.
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Room-temperature liquid metal is a very ideal material for the design of catalytic materials. At low temperatures, the liquid metal enters the liquid state. It provides an opportunity to utilize the liquid phase in the catalysis, which is far superior to the traditional solid-phase catalyst. Aiming at the low performance and narrow application scope of the existing single-phase liquid metal catalyst, this paper proposed a type of liquid metal/metal oxide core-shell composite multi-metal catalyst. The Ga2O3 core-shell heterostructure was formed by chemical modification of liquid metals with different nano metals Cu/W/Mo/Ni, and it was applied to photocatalytic degrading organic contaminated raw liquor. The effects of different metal species on the rate of catalytic degradation were explored. The selectivity and stability of the LM/MO core-shell composite catalytic material were clarified, and it was found that the Ni-LM catalyst could degrade methylene blue and Congo red by 92% and 79%, respectively. The catalytic mechanism and charge transfer mechanism were revealed by combining the optical band gap value. Finally, we provided a theoretical basis for the further development of liquid metal photocatalytic materials in the field of new energy environments.
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Hersam, Mark C. "(Invited) Stabilizing and Enhancing Lithium-Ion Batteries with Chemically Inert 2D Materials." ECS Meeting Abstracts MA2022-01, no. 12 (July 7, 2022): 856. http://dx.doi.org/10.1149/ma2022-0112856mtgabs.
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Efficient energy storage systems represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Arguably, the most important advance in energy storage over the past three decades is the lithium-ion battery, which was recently recognized with the Nobel Prize in Chemistry. However, despite its many successes, issues related to safety, energy density, charging time, and operating temperature range have hindered the realization of the full potential of lithium-ion battery technology, particularly in large-scale applications such as grid-level storage and full electrification of transportation networks. Nanostructured materials were once thought to present compelling opportunities for next-generation lithium-ion batteries, but inherent problems related to high surface area to volume ratios at the nanometer-scale (e.g., undesirable surface chemical interactions between electrodes and electrolytes) have impeded their adoption for commercial applications. This talk will explore how the chemical inertness of select two-dimensional (2D) materials are driving a resurgence in nanostructured lithium-ion battery materials [1]. For example, conformal graphene coatings on lithium-ion battery cathode powders mitigate surface degradation and minimize the formation of the solid electrolyte interphase, thus improving cycling stability [2]. In addition, the high electrical conductivity of graphene reduces cell impedance, resulting in enhanced kinetics that enable high-rate capability and low-temperature performance down to –20 °C [3]. On the other hand, ionogel electrolytes based on ionic liquids and hexagonal boron nitride (hBN) nanoplatelets provide safe, high-rate operation at high temperatures up to 175 °C, which represents the highest operating temperature to date for solid-state lithium-ion batteries [4,5]. The strong interfacial interactions between hBN and ionic liquids further enable novel electrolyte architectures based on layered heterostructure ionogels that result in unprecedently high energy densities and rate performance for solid-state batteries [6]. [1] H. Bergeron, et al., Chemical Reviews, 121, 2713 (2021). [2] K.-Y. Park, et al., Advanced Energy Materials, 10, 2001216 (2020). [3] K.-Y. Park, et al., Advanced Materials, DOI: 10.1002/adma.202106402 (2021). [4] W. J. Hyun, et al., ACS Nano, 13, 9664 (2019). [5] W. J. Hyun, et al., Advanced Energy Materials, 10, 2002135 (2020). [6] W. J. Hyun, et al., Advanced Materials, 33, 2007864 (2021).
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Junk, Yannik, Mingshan Liu, Marvin Frauenrath, Jean-Michel Hartmann, Detlev Gruetzmacher, Dan Buca, and Qing-Tai Zhao. "Vertical GeSn/Ge Heterostructure Gate-All-Around Nanowire p-MOSFETs." ECS Meeting Abstracts MA2022-01, no. 29 (July 7, 2022): 1285. http://dx.doi.org/10.1149/ma2022-01291285mtgabs.
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In recent years, Ge-based group-IV alloys (GeSn, SiGeSn) have received a significant amount of attention as candidates to replace Silicon for future low power and high performance nanoelectronics [1]. The interest in these materials stems primarily from the fact that, by varying the Sn-content of the alloy, it is possible to precisely tune its bandgap from indirect to direct [2], which even opens up the possibility to switch the carrier transport from larger mass low mobility L-valley electrons to the lower mass and high mobility Γ-valley electrons. Adding Si atoms into GeSn alloys enables additional strain engineering by decoupling the lattice constant from the band gap and enables the fabrication of devices to target specific applications. Ge exhibits superior hole mobility over Si and GeSn is predicted to further improve carrier mobilities for both electrons and holes, while still retaining Si CMOS compatibility [3]. In this Abstract, we present the fabrication and characterization of Ge- and GeSn-based vertical gate-all-around (GAA) nanowire (NW) p-MOSFETs. Multilayer stacks of Ge and GeSn were grown on a Ge virtual substrate (Ge-VS) using industrial CVD reactors and subsequently characterized, confirming the high quality of the alloys. On these GeSn/Ge heterostructures, vertical GAA nanowire FETs were fabricated using a top-down approach. First, nanowires were defined by electron-beam lithography and subsequently etched anisotropically using reactive ion etching (RIE). The diameter of the nanowires was reduced by digital etching, consisting of repeated combined GeOx layer formation by plasma oxidation and removal in diluted HF solution. This way nanowires with a diameter down to 20 nm and a height of 210 nm were fabricated. A two-step process was employed for gate dielectric formation to ensure a low interface trap density: (i), deposition of a thin layer of Al2O3, followed by an O2-plasma post-oxidation step; (ii) deposition of a HfO2 dielectric layer to reach the required EOT (equivalent oxide thickness). TiN deposited by sputtering forms the gate metal. Planarization and isotropic dry etching were performed to remove the TiN on the top of the nanowire. After a second planarization step, NiGe-contacts were formed on the exposed top nanowire by Ni-deposition followed by a forming-gas annealing step. Finally, metal contacts for gate and source/drain were added. The resulting Ge-NW-pMOSFETs exhibit high electrical performances. A low subthreshold slope (SS) of 66 mV/dec, a low drain-induced barrier lowering (DIBL) of 35 mV/V and an I on/I off-ratio of 2.1×106 were measured for nanowires with a diameter of 20 nm. For 65 nm NWs, the I on/I off-ratio improves, which is attributed to the decreased contact resistance on top of the NWs, leading to larger on-currents. The peak transconductance for the Ge NWs reached ~190 µS/µm (V DS=-0.5 V). Adopting a GeSn/Ge-heterostructure, with GeSn on top of the nanowire used as source the device performances are strongly enhanced. The on-current I on was increased by ~32%, mostly due to the reduced contact resistivity of the smaller bandgap of GeSn compared to Ge. It was also observed that adopting GeSn alloys leads to an increase in transconductance, G max, to a respectable value of ~870 µS/µm, almost 3 times larger as reported to date for Ge NWs. Moreover, both SS and DIBL are improved by decreasing the NW diameter as a consequence of improved electrostatic gate control over the channel. These results demonstrate that the incorporation of GeSn into Ge-MOSFET technology yields a significant advantage and confirm its high potential for low-power-high-performance nanoelectronics. Fig. 1: (a) Schematic of the GAA nanowire FET based on a GeSn/Ge-heterostructure. (b) Optical image on the metallic contacts (c) Transfer curve of a Ge nanowire pFET with a diameter of 20 nm. The SS is 68 mV/dec and the DIBL is 35 mV/V. (d) Transfer curves of Ge0.92Sn0.08/Ge nanowire pFETs with a diameter of 65 nm and different EOTs. Acknowledgments The authors acknowledge support from the German BMBF project “SiGeSn NanoFETs”. References: [1] M. Liu et al. ACS Appl. Nano Mater. 4, 94-101 (2021) [2] S. Wirths et al. Nature Photonics 9, 88-92 (2015) [3] J. Kouvetakis, J. Menendez, A. V. G. Chizmeshya: Annu. Rev. Mater. Res. 36:497-554 (2006) Figure 1
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Céline, Bourdillon, Hong Phan Ngoc, Daney de Marcillac Willy, Coolen Laurent, Maître Agnès, and Schwob Catherine. "Manipulation of the fluorescence of nanocrystals by opal-based heterostructures." Journal of Materials Chemistry C 3, no. 37 (2015): 9734–39. http://dx.doi.org/10.1039/c5tc01829c.
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Liu, Ying, Yanjun Fang, Deren Yang, Xiaodong Pi, and Peijian Wang. "Recent progress of heterostructures based on two dimensional materials and wide bandgap semiconductors." Journal of Physics: Condensed Matter 34, no. 18 (March 1, 2022): 183001. http://dx.doi.org/10.1088/1361-648x/ac5310.
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Abstract Recent progress in the synthesis and assembly of two-dimensional (2D) materials has laid the foundation for various applications of atomically thin layer films. These 2D materials possess rich and diverse properties such as layer-dependent band gaps, interesting spin degrees of freedom, and variable crystal structures. They exhibit broad application prospects in micro-nano devices. In the meantime, the wide bandgap semiconductors (WBS) with an elevated breakdown voltage, high mobility, and high thermal conductivity have shown important applications in high-frequency microwave devices, high-temperature and high-power electronic devices. Beyond the study on single 2D materials or WBS materials, the multi-functional 2D/WBS heterostructures can promote the carrier transport at the interface, potentially providing novel physical phenomena and applications, and improving the performance of electronic and optoelectronic devices. In this review, we overview the advantages of the heterostructures of 2D materials and WBS materials, and introduce the construction methods of 2D/WBS heterostructures. Then, we present the diversity and recent progress in the applications of 2D/WBS heterostructures, including photodetectors, photocatalysis, sensors, and energy related devices. Finally, we put forward the current challenges of 2D/WBS heterostructures and propose the promising research directions in the future.
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Joester, Derk, Andrew Hillier, Yi Zhang, and Ty J. Prosa. "Organic Materials and Organic/Inorganic Heterostructures in Atom Probe Tomography." Microscopy Today 20, no. 3 (May 2012): 26–31. http://dx.doi.org/10.1017/s1551929512000260.
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Nano-scale organic/inorganic interfaces are key to a wide range of materials. In many biominerals, for instance bone or teeth, outstanding fracture toughness and wear resistance can be attributed to buried organic/inorganic interfaces. Organic/inorganic interfaces at very small length scales are becoming increasingly important also in nano and electronic materials. For example, functionalized inorganic nanomaterials have great potential in biomedicine or sensing applications. Thin organic films are used to increase the conductivity of LiFePO4 electrodes in lithium ion batteries, and solid electrode interphases (SEI) form by uncontrolled electrolyte decomposition. Organics play a key role in dye-sensitized solar cells, organic photovoltaics, and nano-dielectrics for organic field-effect transistors. The interface between oxide semiconductors and polymer substrates is critical in emergent applications, for example, flexible displays.
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Joshi, Nirav, Maria Luisa Braunger, Flavio Makoto Shimizu, Antonio Riul Jr, and Osvaldo N. Oliveira. "Insights into nano-heterostructured materials for gas sensing: a review." Multifunctional Materials 4, no. 3 (August 23, 2021): 032002. http://dx.doi.org/10.1088/2399-7532/ac1732.
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Bharadwaj, Sathwik, Ashwin Ramasubramaniam, and L. R. Ram-Mohan. "Non-asymptotic quantum scattering theory to design high-mobility lateral transition-metal dichalcogenide heterostructures." Journal of Applied Physics 131, no. 17 (May 7, 2022): 174302. http://dx.doi.org/10.1063/5.0089639.
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Atomistic determination of carrier scattering properties is essential for designing nano-electronic devices in two-dimensional (2D) materials. Traditional quantum scattering theory is developed in an asymptotic limit, thus making it inapplicable for 2D materials and heterostructures. Here, we introduce a new paradigm of non-asymptotic quantum scattering theory to obtain the carrier scattering properties at finite distances from active scattering centers. We develop an atomistic multiscale formalism built on the [Formula: see text] Hamiltonian, supplemented with parameters from first-principles electronic structure calculations. We apply this framework to investigate electron transport in lateral transition-metal dichalcogenide heterostructures and demonstrate enhanced high mobility of the order of [Formula: see text] at room temperature. The non-asymptotic quantum scattering formalism provides a new frontier to design high-performance mesoscopic devices in 2D materials.
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Mezzacappa, Marc, Dheyaa Alameri, Brian Thomas, Yoosuk Kim, Chi-Hou Lei, and Irma Kuljanishvili. "In Situ Measurements of Strain Evolution in Graphene/Boron Nitride Heterostructures Using a Non-Destructive Raman Spectroscopy Approach." Nanomaterials 12, no. 17 (September 3, 2022): 3060. http://dx.doi.org/10.3390/nano12173060.
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The mechanical properties of engineered van der Waals (vdW) 2D materials and heterostructures are critically important for their implementation into practical applications. Using a non-destructive Raman spectroscopy approach, this study investigates the strain evolution of single-layer graphene (SLGr) and few-layered boron nitride/graphene (FLBN/SLGr) heterostructures. The prepared 2D materials are synthesized via chemical vapor deposition (CVD) method and then transferred onto flexible polyethylene terephthalate (PET) substrates for subsequent strain measurements. For this study, a custom-built mechanical device-jig is designed and manufactured in-house to be used as an insert for the 3D piezoelectric stage of the Raman system. In situ investigation of the effects of applied strain in graphene detectable via Raman spectral data in characteristic bonds within SLGr and FLBN/SLGr heterostructures is carried out. The in situ strain evolution of the FLBN/SLGr heterostructures is obtained in the range of (0–0.5%) strain. It is found that, under the same strain, SLG exhibits a higher Raman shift in the 2D band as compared with FLBN/SLGr heterostructures. This research leads to a better understanding of strain dissipation in vertical 2D heterostacks, which could help improve the design and engineering of custom interfaces and, subsequently, control lattice structure and electronic properties. Moreover, this study can provide a new systematic approach for precise in situ strain assessment and measurements of other CVD-grown 2D materials and their heterostructures on a large scale for manufacturing a variety of future micro- and nano-scale devices on flexible substrates.
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., Amardeep, and Vijay Kr Lamba. "Study and Modeling of Graphene-Boron-Nitride Heterostructures." SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 14, no. 03 (July 15, 2022): 337–40. http://dx.doi.org/10.18090/samriddhi.v14i03.14.
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When we talk about nano devices, the molecule and its interface with electrodes play a key role. So, one of the major objectives is to select an organic nanomaterial with extensive applications, which requires smart synthesis of appropriate materials and an understanding of their properties. Here we modeled a device, which not only adds another “protuberance” to learn about the transport properties of the molecule but also helps in grasping its use as a considerable material for future flexible electronics. Modeling of materials at the nano-level not only provides fundamental insight into the properties of crystalline defects but also gives a reasonable understanding of phase stability and learning of processes like atomic diffusion interface migration. For the development of devices at a mesoscopic and macroscopic level and with atomistic input parameters, this recognition serves as a guide. We tried to model how the layers of one type of molecule and the interaction of two different types of molecular layers control the junction charge transport characteristics.
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Kuznetsov, Alexey, Prithu Roy, Valeriy M. Kondratev, Vladimir V. Fedorov, Konstantin P. Kotlyar, Rodion R. Reznik, Alexander A. Vorobyev, Ivan S. Mukhin, George E. Cirlin, and Alexey D. Bolshakov. "Anisotropic Radiation in Heterostructured “Emitter in a Cavity” Nanowire." Nanomaterials 12, no. 2 (January 13, 2022): 241. http://dx.doi.org/10.3390/nano12020241.
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Tailorable synthesis of axially heterostructured epitaxial nanowires (NWs) with a proper choice of materials allows for the fabrication of novel photonic devices, such as a nanoemitter in the resonant cavity. An example of the structure is a GaP nanowire with ternary GaPAs insertions in the form of nano-sized discs studied in this work. With the use of the micro-photoluminescence technique and numerical calculations, we experimentally and theoretically study photoluminescence emission in individual heterostructured NWs. Due to the high refractive index and near-zero absorption through the emission band, the photoluminescence signal tends to couple into the nanowire cavity acting as a Fabry–Perot resonator, while weak radiation propagating perpendicular to the nanowire axis is registered in the vicinity of each nano-sized disc. Thus, within the heterostructured nanowire, both amplitude and spectrally anisotropic photoluminescent signals can be achieved. Numerical modeling of the nanowire with insertions emitting in infrared demonstrates a decay in the emission directivity and simultaneous rise of the emitters coupling with an increase in the wavelength. The emergence of modulated and non-modulated radiation is discussed, and possible nanophotonic applications are considered.
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Babar, Zaheer Ud Din, Ali Raza, Antonio Cassinese, and Vincenzo Iannotti. "Two Dimensional Heterostructures for Optoelectronics: Current Status and Future Perspective." Molecules 28, no. 5 (February 28, 2023): 2275. http://dx.doi.org/10.3390/molecules28052275.
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Researchers have found various families of two-dimensional (2D) materials and associated heterostructures through detailed theoretical work and experimental efforts. Such primitive studies provide a framework to investigate novel physical/chemical characteristics and technological aspects from micro to nano and pico scale. Two-dimensional van der Waals (vdW) materials and their heterostructures can be obtained to enable high-frequency broadband through a sophisticated combination of stacking order, orientation, and interlayer interactions. These heterostructures have been the focus of much recent research due to their potential applications in optoelectronics. Growing the layers of one kind of 2D material over the other, controlling absorption spectra via external bias, and external doping proposes an additional degree of freedom to modulate the properties of such materials. This mini review focuses on current state-of-the-art material design, manufacturing techniques, and strategies to design novel heterostructures. In addition to a discussion of fabrication techniques, it includes a comprehensive analysis of the electrical and optical properties of vdW heterostructures (vdWHs), particularly emphasizing the energy-band alignment. In the following sections, we discuss specific optoelectronic devices, such as light-emitting diodes (LEDs), photovoltaics, acoustic cavities, and biomedical photodetectors. Furthermore, this also includes a discussion of four different 2D-based photodetector configurations according to their stacking order. Moreover, we discuss the challenges that remain to be addressed in order to realize the full potential of these materials for optoelectronics applications. Finally, as future perspectives, we present some key directions and express our subjective assessment of upcoming trends in the field.
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Kitaura, Ryo. "(Invited, Digital Presentation) Ultrathin Lateral Heterostructures Based on Two-Dimensional Semiconductors." ECS Meeting Abstracts MA2022-01, no. 10 (July 7, 2022): 784. http://dx.doi.org/10.1149/ma2022-0110784mtgabs.
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Low-dimensional (2D) materials, including carbon nanotubes, graphene, boron nitrides, and transition metal dichalcogenides (TMDs), have provided a platform to explore novel physics at the nano-scale. In addition to the fascinating properties of low-dimensional materials themselves, they allow exploring novel superstructures, such as heterojunctions, heterostacks, and superlattices, which give even broader possibilities. We are working on low-dimensional superstructures fabricated by (1) crystal growth with metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), and (2) stacking each component with the full-dry-transfer-based manipulation technique[1]-[6]. This presentation will focus on our recent works on low-dimensional superstructures, such as 2D ultrathin lateral superlattices. For example, we have successfully realized MoS2/WS2 2D lateral superlattices with a periodicity of down to one-atom-thick by MOCVD with an automatic valve control system. Also, we have observed characteristic PL arising probably from 1D junction structures. More details on the fabrication and optical properties of these superstructures will be addressed in this talk. [1] Y. Murai, et. al., ACS Nano 2021, doi.org/10.1021/ascnano.1c04584 [2] T. Hotta, et. al., ACS Nano 2021, 51:1370-1377. [3] T. Hotta, et al., Phys. Rev. B 2020, 102:115424. [4] S. Zhao et al., Phys. Rev. Lett. 2020, 124:106101. [5] Y. Uchiyama et. al., npj 2D Mater. App. 2019, 3:26. [6] M. Okada, et. al., ACS Nano 2018, 12:2498-2505.
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Wang, Ka, Haizeng Song, Zixia Lin, Yuan Gao, Han Wu, Shancheng Yan, Jun Wang, and Yi Shi. "Improving hydrogen evolution performance of Co:FeS2/CoS2 nano-heterostructure at elevated temperatures." Materials Express 9, no. 7 (October 1, 2019): 786–91. http://dx.doi.org/10.1166/mex.2019.1558.
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Fabrication and improvement of high-efficient, durable, and earth-abundant non-precious metal hydrogen evolution electrocatalysts are particularly important in the production of clean energy hydrogen. In this study, we synthesized Co:FeS2/CoS2 nano-heterostructure with superior hydrogen evolution performance by a typical one-step hydrothermal method. When the temperature of HER solution was raised from 0 °C to 60 °C, the overpotential for Co:FeS2/CoS2 nano-heterostructure at 10 cm–2 was reduced from 115 to 75 mV and its Tafel slope did not change significantly. Moreover, the overpotential for Co:FeS2/CoS2 nano-heterostructure increased by only 6 mV after 1000 cycles of CV at 60 °C. This work provides a strategy for preparing and improving the performance of non-precious metal electrocatalysts to replace precious metal electrocatalysts.
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Doeff, Marca M., Wei Yin, and Gozde Barim. "(Invited) Developing Titanate Anodes for Sodium Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 2 (October 9, 2022): 127. http://dx.doi.org/10.1149/ma2022-022127mtgabs.
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Sodium titanates are among the most promising anode materials for sodium ion batteries, due to their low cost, possibility of high tap density, and relatively higher operation voltage compared to commonly used hard carbons that prevents metallic sodium plating. 1 However, these oxides have a finite number of sites for ion insertion, which limits the Na+storage capacity, and thereby the achievable energy density. The sluggish Na+ (de)intercalation kinetics and poor electronic conductivity are other impediments to the practical capacity and rate capability. The presence of mobile cations (e.g., Li+) instead of less mobile ones (e.g., Mg2+) in the metal oxide layers was shown to provide additional diffusional pathways for Na+ and improves the practical capacities.2 This observation motivated us to design and synthesize lepidocrocite-structured titanates with vacancies in the metal oxide layers, on the assumption that these vacancies will have similar beneficial effects as mobile cations.3 These non-stoichiometric titanates do indeed show improved capacities, due to the additional sites in the metal oxide layers, and, possibly, some surface contributions to the redox behavior. To overcome kinetic limitations, large amounts of carbon additives are often used to improve electrical conductivity in the electrode composites. However, it is possible to manipulate the titanate structure instead, by incorporating conductive carbon between the metal oxide layers to overcome the electronic limitations. To this end, we have designed and synthesized heterostructures of lepidocrocite titanates.4 Carbon-free composite electrodes containing these heterostructures outperform conventional titanate electrodes containing carbon, illustrating the principle. References: Rudola, A.; Rennie, A. J. R.; Heap, R.; Meysami, S. S.; Lowbridge, A.; Mazzali, F.; Sayers, R.; Wright, C. J.; Barker, J., Commercialisation of high energy density sodium-ion batteries: Faradion's journey and outlook. Journal of Materials Chemistry A 2021, 9 (13), 8279-8302. Markus, I. M.; Engelke, S.; Shirpour, M.; Asta, M.; Doeff, M., Experimental and Computational Investigation of Lepidocrocite Anodes for Sodium-Ion Batteries. Chemistry of Materials 2016, 28 (12), 4284-4291. Yin, W.; Alvarado, J.; Barim, G.; Scott, M. C.; Peng, X.; Doeff, M. M., A layered nonstoichiometric lepidocrocite-type sodium titanate anode material for sodium-ion batteries. MRS Energy & Sustainability 2021. Barim, G.; Dhall, R.; Arca, E.; Kuykendall, T. R.; Yin, W.; Takeuchi, K. J.; Takeuchi, E. S.; Marschilok, A. C.; Doeff, M. M., Heterostructured Lepidocrocite Titanate-Carbon Nanosheets for Electrochemical Applications. ACS Applied Nano Materials 2021, 5 (1), 678-690.
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Akbar, Sheikh Ali. "(Invited) Ceramic Nano-Heterostructures By Materials Design: Platforms for Sensing Applications – Opportunities and Challengess." ECS Meeting Abstracts MA2022-01, no. 52 (July 7, 2022): 2141. http://dx.doi.org/10.1149/ma2022-01522141mtgabs.
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This talk summarizes R&D efforts in the author’s laboratory on the fabrication of oxide nano-heterostructures, exploiting intrinsic material properties, that are highly scalable and do not require use of lithography. One such process creates crystallographically oriented nanofiber arrays of single crystal TiO2 in H2/N2 environment. H2/N2 heat treatment was also used to grow nanofibers on polycrystalline SnO2, showing directional growth on grains with crystal facets. We have also developed a process to create nanofibers of TiO2 on Ti metal/alloys via oxidation under a limited supply of oxygen. In another process, SnO2 nanowires grown from commercial FTO slides using the vapor-liquid-solid (VLS) method were placed in a microwave-assisted hydrothermal chamber where TiO2 nanorods nucleated radially from the SnO2 nanowire cores. We developed yet another interesting nano-structure (nanoislands and/or nanobars) during thermal annealing of an oxide (GDC) on top of another oxide (YSZ) substrate that self-assembles along the softest elastic direction of the substrate. What is common about these structures is that they are fabricated without the use of lithographic techniques and involves simple processes such as gas-phase reactions and stress-driven processes. These nano-heterostructures can be used as platforms for chemical sensing, catalysis, photocatalysis, photovoltaics and biomedical applications. Sensing application presents opportunities and challenges that are presented including an Open access Database Of Resistive type gas Sensors (ODORS) that has been developed and can be used to select suitable sensing materials.
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Tatsuoka, Hirokazu, Wen Li, Er Chao Meng, Daisuke Ishikawa, and Kaito Nakane. "Syntheses and Structural Control of Silicide, Oxide and Metallic Nano-Structured Materials." Solid State Phenomena 213 (March 2014): 35–41. http://dx.doi.org/10.4028/www.scientific.net/ssp.213.35.
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The structural control and morphological modification of a series of silicide, oxide and Ag metal nanostructures have been further discussed with reviews of nanostructure syntheses, such as CrSi2 nanowire bundles dendrites, MoSi2 nanosheets, α-Fe2O3 nanowires nanobelts, CuO/Cu2O nanowire axial heterostructures, ZrO2/SiOx and CrSi2/SiOx core/shell nanowires. In addition, the syntheses of Ag three-dimensional dendrites, two-dimensional dendrites, two-dimensional fractal structures, particles and nanowires also were discussed. Moreover, the structural and morphological properties of the nanostructures were examined. The structural control and morphological modifications of the nanostructures have been successfully demonstrated by the appropriate thermal treatments with specific starting materials. A large volume of silicide nanowire bundles, large area of oxide nanowire arrays and large area Ag nanostructure coatings were successfully fabricated.
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Chang, Kai-Ping, Kuan-I. Ho, Mohamed Boutchich, Julien Chaste, Hakim Arezki, and Chao-Sung Lai. "Graphene/fluorographene heterostructure for nano ribbon transistor channel." Semiconductor Science and Technology 35, no. 1 (November 28, 2019): 015005. http://dx.doi.org/10.1088/1361-6641/ab52ed.
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Drewniak, Sabina Elżbieta, and Łukasz Drewniak. "The influence of the type of graphite on the size of reduced graphene oxide." Photonics Letters of Poland 14, no. 2 (July 1, 2022): 34. http://dx.doi.org/10.4302/plp.v14i2.1153.
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Reduced graphene oxide is a very attractive material for sensor applications. It exhibits high conductivity at room temperature and high specific surface area. Since it can be produced in many ways, its properties can be influenced by the fabrication method. In this paper, we investigated the influence of graphite precursors (flake, scalar and synthetic) on the size of reduced graphene oxide. We have shown that the size of the precursor determines the size of the obtained rGO. We have noted that the larger graphite size, the larger rGO size. Full Text: PDF ReferencesR. Peng, Y. Li, T. Liu et al., "Reduced graphene oxide/SnO2@Au heterostructure for enhanced ammonia gas sensing", Chem. Phys. Lett., 737, 136829 (2019). CrossRef S. Pei and H. M. Cheng, "The reduction of graphene oxide", Carbon N. Y., 50, 9 (2012). CrossRef N. Sharma, V. Sharma, R. Vyas et al., "A new sustainable green protocol for production of reduced graphene oxide and its gas sensing properties", J. Sci. Adv. Mater. Devices, 4, 3 (2019) CrossRef R. Tarcan, O. Todor-Boer, I. Petrovai, C. Leordean, S. Astilean, I. Botiz, "Reduced graphene oxide today", J. Mater. Chem. C, 8, 4 (2020). CrossRef X. Jiao, Y. Qiu, L. Zhang, and X. Zhang, "Comparison of the characteristic properties of reduced graphene oxides synthesized from natural graphites with different graphitization degrees", RSC Adv., 7, 82 (2017). CrossRef J.A. Quezada-Renteria, C.O. Ania, L.F. Chazaro-Ruiz, J.R. Rangel-Mendez, "Influence of protons on reduction degree and defect formation in electrochemically reduced graphene oxide", Carbon N. Y., 149 (2019). CrossRef H. Gao, Y. Ma, P. Song, J. Leng, Q. Wang, "Characterization and cytocompatibility of 3D porous biomimetic scaffold derived from rabbit nucleus pulposus tissue in vitro", J. Mater. Sci. Mater. Electron., 32, 8 (2021). CrossRef A.T. Lawal, "Graphene-based nano composites and their applications. A review", Biosens. Bioelectron., 141, 111384, (2019). CrossRef E. Aliyev, V. Filiz, M.M. Khan, Y.J. Lee, C. Abetz, V. Abetz, "Structural Characterization of Graphene Oxide: Surface Functional Groups and Fractionated Oxidative Debris", Nanomaterials, 9, 8 (2019). CrossRef S. Sali, H.R. Mackey, A.A. Abdala, "Effect of Graphene Oxide Synthesis Method on Properties and Performance of Polysulfone-Graphene Oxide Mixed Matrix Membranes", Nanomaterials, 9, 5 (2019). CrossRef G. Lu, L.E. Ocola, J. Chen, "Reduced graphene oxide for room-temperature gas sensors", Nanotechnology, 20, 44 (2009). CrossRef C. Botas, P. Alvarez, C. Blanco et al., "Critical temperatures in the synthesis of graphene-like materials by thermal exfoliation–reduction of graphite oxide", Carbon N. Y., 52, 2013. CrossRef
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Zimmermann, T., M. Kubovic, A. Denisenko, K. Janischowsky, O. A. Williams, D. M. Gruen, and E. Kohn. "Ultra-nano-crystalline/single crystal diamond heterostructure diode." Diamond and Related Materials 14, no. 3-7 (March 2005): 416–20. http://dx.doi.org/10.1016/j.diamond.2004.12.049.
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Dinelli, Franco, Filippo Fabbri, Stiven Forti, Camilla Coletti, Oleg V. Kolosov, and Pasqualantonio Pingue. "Scanning Probe Spectroscopy of WS2/Graphene Van Der Waals Heterostructures." Nanomaterials 10, no. 12 (December 11, 2020): 2494. http://dx.doi.org/10.3390/nano10122494.
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In this paper, we present a study of tungsten disulfide (WS2) two-dimensional (2D) crystals, grown on epitaxial Graphene. In particular, we have employed scanning electron microscopy (SEM) and µRaman spectroscopy combined with multifunctional scanning probe microscopy (SPM), operating in peak force–quantitative nano mechanical (PF-QNM), ultrasonic force microscopy (UFM) and electrostatic force microscopy (EFM) modes. This comparative approach provides a wealth of useful complementary information and allows one to cross-analyze on the nanoscale the morphological, mechanical, and electrostatic properties of the 2D heterostructures analyzed. Herein, we show that PF-QNM can accurately map surface properties, such as morphology and adhesion, and that UFM is exceptionally sensitive to a broader range of elastic properties, helping to uncover subsurface features located at the buried interfaces. All these data can be correlated with the local electrostatic properties obtained via EFM mapping of the surface potential, through the cantilever response at the first harmonic, and the dielectric permittivity, through the cantilever response at the second harmonic. In conclusion, we show that combining multi-parametric SPM with SEM and µRaman spectroscopy helps to identify single features of the WS2/Graphene/SiC heterostructures analyzed, demonstrating that this is a powerful tool-set for the investigation of 2D materials stacks, a building block for new advanced nano-devices.
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Lu, Yang-Ming, Chi-Feng Tseng, Bing-Yi Lan, and Chia-Fen Hsieh. "Fabrication of Graphene/Zinc Oxide Nano-Heterostructure for Hydrogen Sensing." Materials 14, no. 22 (November 17, 2021): 6943. http://dx.doi.org/10.3390/ma14226943.
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In this study, hydrogen (H2) and methane (CH4) were used as reactive gases, and chemical vapor deposition (CVD) was used to grow single-layer graphene on a copper foil substrate. The single-layer graphene obtained was transferred to a single-crystal silicon substrate by PMMA transfer technology for the subsequent growth of nano zinc oxide. The characteristics of CVD-deposited graphene were analyzed by a Raman spectrometer, an optical microscope, a four-point probe, and an ultraviolet/visible spectrometer. The sol–gel method was applied to prepare the zinc oxide seed layer film with the spin-coating method, with methanol, zinc acetate, and sodium hydroxide as the precursors for growing ZnO nanostructures. On top of the ZnO seed layer, a one-dimensional zinc oxide nanostructure was grown by a hydrothermal method at 95 °C, using a zinc nitrate and hexamethylenetetramine mixture solution. The characteristics of the nano zinc oxide were analyzed by scanning electron microscope(SEM),x-ray diffractometer(XRD), and Raman spectrometer. The obtained graphene/zinc oxide nano-heterostructure sensor has a sensitivity of 1.06 at a sensing temperature of 205 °C and a concentration of hydrogen as low as 5 ppm, with excellent sensing repeatability. The main reason for this is that the zinc oxide nanostructure has a large specific surface area, and many oxygen vacancy defects exist on its surface. In addition, the P–N heterojunction formed between the n-type zinc oxide and the p-type graphene also contributes to hydrogen sensing.
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Camellini, Andrea, Haiguang Zhao, Sergio Brovelli, Ranjani Viswanatha, Alberto Vomiero, and Margherita Zavelani-Rossi. "(Invited) Ultrafast Spectroscopy in Semiconductor Nanocrystals: Revealing the Origin of Single Vs Double Emission, of Optical Gain and the Role of Dopants." ECS Meeting Abstracts MA2022-01, no. 20 (July 7, 2022): 1104. http://dx.doi.org/10.1149/ma2022-01201104mtgabs.
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A wide variety of materials with nanometre dimensions are increasingly explored for photonic applications. Among them, semiconductor nanocrystals (NCs) are very promising for a variety of uses, including light emission devices (LEDs), lasers, detectors, photovoltaic cells, biological labelling and sensing [1]. Key advantage of NCs is the possibility to tailor their optical response by controlling the electronic structure (“wave function engineering”) through the choice of composition, size and shape. Significant and interesting results have been obtained with heterostructured and doped NCs. Beyond single wavelength tuneable band-edge emission, other regimes have been demonstrated such as intragap emission, simultaneous emission on two different wavelengths, amplified spontaneous emission and laser emission. The luminescent properties are governed by exciton decay, which can proceed through radiative or nonradiative pathways, following different routes. The study of exciton dynamics can allow elucidating the processes connected to single or dual emission and to optical gain. This, in turn, can lead to the identification of the functional and structural characteristics that are responsible for these behaviors. Exciton relaxation occurs on picosecond timescales, so ultrafast optical techniques are required to perform these studies. In this talk, we present studies carried out by ultrafast pump-probe spectroscopy technique, with 100-fs time resolution, on CdSe/CdS and PbS/CdS heterostructured NCs, with different geometries (core/shell, dot-in-rod, dot-in-bulk, with sharp or graded interface) [2-6] and CdSeS and CdZnSe doped NCs [7,8]. These NCs are optically active in the visible and near-infrared spectral region, show single and dual colour photoluminescence emission, optical gain, laser emission and intragap emission [2-9]. The analysis of the experimental data allowed us to unravel the decay processes: the initials take place in a few ps, leading to the ultimate emitting state whose lifetime can extend to hundreds of ps to few ns, allowing for efficient luminescence and optical gain. Our data on heterostructures allowed us to clarify the role of the volume and of the shape of the outer component and the effect of the interface [2-4]. We found that dual emission is possible for both thick and thin quantum-confined shells, and for different interfaces. We studied the decoupling of excitons lying in the two different component of the NC (core exciton and shell exciton) and we revealed the evolution of the exciton barrier known as dynamic hole-blockade effect. We showed that these phenomena are strictly connected to dual emission and optical gain and we identified the condition for their maximum efficiency, in term of band alignment and band transitions. Our results provide a comprehensive understanding of the physical phenomena governing dual-emission mechanisms, suppression of Auger recombination, optical gain and laser emission in heterostructured NCs. Experiments on CdZnSe NCs doped with Mn and on CdSeS NCs engineered with sulfur vacancies, enabled us to disclose donor and acceptor localized states in the band gap. We observed the carrier dynamics responsible for intragap emission which is associated to the emergence of a transient Mn3+ state [7], in the first case, and to a donor state below the conduction band introduced by sulfur vacancies [8], in the latter case. In conclusion, the study of the exciton dynamics in different NCs allowed us to elucidate the relation between structural-morphological characteristics (shape, volume, and interface) and unconventional emission capabilities (dual emission and optical gain) in heterostructures and the photophysics of electronic states introduced by doping. This knowledge is very important to control NC functionalities toward new multilevel electronic or photonic schemes and in applications such as lasers [9], photoelectrochemical (PEC) cell [10], white light emission [11], ratiometric sensing [12]. [1] P. V. Kamat and G. D. Scholes, J. Phys. Chem. Lett. 7, 584 (2016) [2] G. Sirigu et al., Phys. Rev. B 96, 155303 (2017) [3] V. Pinchetti et al., ACS Nano 10, 6877-6887 (2016) [4] H. Zhao et al., Nanoscale 8, 4217-4226 (2016) [5] M. Zavelani-Rossi et al., Nano Lett. 10, 3142-3150 (2010) [6] R. Krahne et al., Appl. Phys. Lett. 98, 063105 (2011) [7] K. Gahlot et al., ACS Energy Lett. 4, 729−735 (2019) [8] F. Carulli et al., Nano Lett. 21, 6211−6219 (2021) [9] M. Zavelani-Rossi et al., Laser & Photonics Reviews 6, 678-683 (2012) [10] L. Jin et al., Nano Energy 30, 531-541 (2016) [11] S. Sapra et al., Adv. Mater. 19, 569 (2007) [12] J. Liu et al., ACS Photonics, 2479 (2019)
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Lyu, Wei, Hanchao Teng, Chenchen Wu, Xiaotao Zhang, Xiangdong Guo, Xiaoxia Yang, and Qing Dai. "Anisotropic acoustic phonon polariton-enhanced infrared spectroscopy for single molecule detection." Nanoscale 13, no. 29 (2021): 12720–26. http://dx.doi.org/10.1039/d1nr01701b.
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Li, Benxia, and Yanfen Wang. "Synthesis, microstructure, and photocatalysis of ZnO/CdS nano-heterostructure." Journal of Physics and Chemistry of Solids 72, no. 10 (October 2011): 1165–69. http://dx.doi.org/10.1016/j.jpcs.2011.07.010.
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Sanjay, Sooraj, Fahimul Islam Sakib, Mainul Hossain, and Navakanta Bhat. "(Invited, Digital Presentation) Super-Nernstian Isfet Combining Two-Dimensional WSe2/MoS2 Heterostructure with Negative Capacitance." ECS Meeting Abstracts MA2022-02, no. 15 (October 9, 2022): 823. http://dx.doi.org/10.1149/ma2022-0215823mtgabs.
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Ion-sensitive field-effect transistors (ISFETs) are quite popular as compact, low-cost biosensors with fast response time and label-free detection1. They can be used as pH sensors or functionalized for complex biomolecule detection. The voltage sensitivity (Sv) in classical ISFETs is fundamentally limited to 59 mV/pH (Nernst limit). Surpassing the Nernst limit requires complex device architectures or novel transport phenomena. Sensitivity beyond the Nernst limit can be achieved using specific device architectures such as dual gate ISFETs2, negative capacitance ISFETs (NC-ISFET)3, tunnel ISFETs4, etc. Compatible architectures can be combined for further enhancements in sensitivity. First, we experimentally demonstrate a super-Nernstian hetero-ISFET that uses 2-D WSe2/MoS2 heterostructure in a double-gated configuration5. The schematic of the device structure is shown in Fig. 1(a) along with its dimensions. The fluid gate to the pH solution is biased at VFG = 0 V and the voltage sensitivity (SV) is extracted by applying bias to the back-gate (VBG). Fig. 1(b) shows the variation of drain current for change in VBG at different pH. The voltage sensitivity is also included in the same graph. The device uses charge screening due to the interface traps and inversion charges at the hetero-interface to modulate the back-gate transconductance (gmb), thereby allowing super sensitivity. Further enhancement in sensitivity is explored using technology computer-aided (TCAD) device simulator tool (Silvaco ATLAS) by integrating with different device architectures. First we model the baseline hetero-ISFET. The 2-D materials were modeled using their material parameters and 3-D equivalents of their density of states. Amorphous hafnium oxide (HfO2) was used as the dielectric. The mobile ions in the electrolyte were modeled as charge carriers in an intrinsic semiconductor, with its effective density of states varying as a function of pH. The simulation model was calibrated with the experimental device (at pH = 7), as shown in Fig. 2(a). The transfer characteristics of the back-gate at different pH and fixed VFG (= 0 V) for the simulated device is shown in Fig. 2(b). We note that the sensitivity from simulations is lower than the experimental device. This is likely due to non-ideal and 2-D material specific factors which are not accounted in simulations. Nevertheless, the simulated device also shows super-Nernstian sensitivity (Fig. 2(b), right axis), validating the model. Hence, the calibrated TCAD model is used as the baseline for further studies. Next, an NC-FE layer (aluminum-doped HfO2) was added to the top fluid-gate stack6. We have used a ferroelectric-metal-insulator-semiconductor (FMIS) stack for the proposed NC-hetero-ISFET. Fig. 3(a) shows the new top-gate stack with the FMI layer, which replaces the top-gate stack in the earlier schematic. The fluid-gate charge (QFG), and drain current (ID) as a function of VFG (VBG = 0 V), were obtained from the TCAD simulations. The 1-D Landau–Khalatnikov (L-K) equations were used to model the voltage across the FE layer (VFE = 2αQFG+4βQ3 FG = V' FG - Vint; where V' FG is the newly computed fluid-gate bias and Vint is the internal node voltage)7. The calculated Vint (for fixed V' FG) is coupled back into the ATLAS simulator to extract voltage sensitivity (SV) by sweeping VBG at different pH values. The fluid-gate transfer curve of the proposed NC-hetero-ISFET, in Fig. 3(b), clearly shows a steeper sub-threshold slope and higher ON current than the baseline device. The corresponding FE layer parameters are shown in Table 1. These improved fluid-gate characteristics contribute to an increased voltage-sensitivity (SV) when VBG is applied. The transfer characteristic (ID v/s VBG, at fixed V' FG) of the NC-hetero-ISFET at different pH values is shown in Fig. 3(c), along with the voltage sensitivity. Further, in Fig. 3(d), we compare the peak SV obtained at different V' FG. There is an improvement in voltage sensitivity (as much as ~ 100 mV/pH) over the baseline device when NC is introduced. The results pave the way for highly sensitive super-Nernstian ISFETs by combining 2-D heterostructure with NC effect. References: P. Bergveld, Sensors Actuators, B Chem., 88, 1–20 (2003). M. Spijkman et al., Appl. Phys. Lett., 98, 2011–2014 (2011). F. Bellando et al., Appl. Phys. Lett., 116, 173503 (2020) P. Dwivedi, R. Singh, and Y. S. Chauhan, IEEE Sens. J., 21, 3233–3240 (2021). S. Sanjay, M. Hossain, A. Rao, and N. Bhat, npj 2D Mater. Appl. 2021 51, 5, 1–8 (2021) S. Salahuddin and S. Datta, Nano Lett, 8, 405–410 (2008) F. I. Sakib, M. A. Hasan, and M. Hossain, IEEE Trans. Electron Devices, 69, 311–317 (2022). Figure 1
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Ahmad, Jahangir, Malik Wahid, and Kowsar Majid. "In situ construction of hybrid MnO2@GO heterostructures for enhanced visible light photocatalytic, anti-inflammatory and anti-oxidant activity." New Journal of Chemistry 44, no. 26 (2020): 11092–104. http://dx.doi.org/10.1039/d0nj00881h.
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Perez de Lara, David. "Hybrid Superconducting/Magnetic Multifunctional Devices in Two-Dimensional Systems." Physchem 2, no. 4 (November 25, 2022): 347–56. http://dx.doi.org/10.3390/physchem2040025.
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The emergence of unexpected properties in two-dimensional materials, interfaces, and nanostructured materials opens an exciting framework for exploring new devices and applications. Recent advances in materials design and the nano structurization of novel, low-dimensional materials, surfaces, and interfaces offer a novel playground to design efficient multifunctional materials-based devices. Low-dimensional materials exhibit peculiarities in their electronic, magnetic, and optical properties, changing with respect to the bulk when they are layered down to a single layer, in addition to their high tunability. Their crystal structure and chemical bonds lead to inherent unique mechanical properties. The fabrication of van der Waals heterostructures by stacking materials with different properties, the better control of interfaces, and the tunability of the physical properties by mechanical strain, and chemical and electronic doping allow for the exploration of multifunctional devices with superconducting, magnetic, and optical properties and unprecedented degrees of freedom in terms of fabrication and tunability.
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Navakoteswara Rao, Vempuluru, Pasupuleti Kedhareswara Sairam, Moon-Deock Kim, Mashallah Rezakazemi, Tejraj M. Aminabhavi, Chi Won Ahn, and Jun-Mo Yang. "CdS/TiO2 nano hybrid heterostructured materials for superior hydrogen production and gas sensor applications." Journal of Environmental Management 340 (August 2023): 117895. http://dx.doi.org/10.1016/j.jenvman.2023.117895.
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Schlykow, Viktoria, Costanza Lucia Manganelli, Friedhard Römer, Caterina Clausen, Lion Augel, Jörg Schulze, Jens Katzer, et al. "Ge(Sn) nano-island/Si heterostructure photodetectors with plasmonic antennas." Nanotechnology 31, no. 34 (June 11, 2020): 345203. http://dx.doi.org/10.1088/1361-6528/ab91ef.
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Hu, Cheng, Aolin Deng, Peiyue Shen, Xingdong Luo, Xianliang Zhou, Tongyao Wu, Xinyue Huang, et al. "Direct imaging of interlayer-coupled symmetric and antisymmetric plasmon modes in graphene/hBN/graphene heterostructures." Nanoscale 13, no. 35 (2021): 14628–35. http://dx.doi.org/10.1039/d1nr03210k.
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We report near-field infrared nano-imaging of plasmon–plasmon coupling in two vertically separated graphene layers in graphene/hBN/graphene heterostructure. Emergent symmetric and anti-symmetric coupling modes are directly observed simultaneously.