Relevant bibliographies by topics / Core-shell Heterostructure

Academic literature on the topic 'Core-shell Heterostructure'

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Published: 7 September 2023

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Journal articles on the topic "Core-shell Heterostructure"

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Gopalan, Srikanth, and Benjamin Levitas. "Heterostructured Functional Materials through Molten Salt Synthesis for Solid Oxide Fuel Cells and Electrolysis Cells." ECS Meeting Abstracts MA2022-01, no. 38 (July 7, 2022): 1679. http://dx.doi.org/10.1149/ma2022-01381679mtgabs.

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La0.6Sr0.4Co0.2Fe0.8O3 (LSCF)−La0.8Sr0.2MnO3 (LSM) heterostructure crystalline materials have been synthesized in a simple, one-step via reaction-deposition process using a molten salt. Two-phase perovskite composites can be synthesized in times as short as 10 minutes in a molten salt solvent. X-ray diffraction and S/TEM energy dispersive X-ray spectroscopy have been utilized to confirm the formation of an LSM shell on LSCF cores in all samples when adjusting dwell time, core size, weight ratio between core and shell precursors, and weight ratio of powder to salt. Specifically, decreasing the LSCF core size increases core−shell yield. Smaller cores result in a greater density of facets on the crystal surface and provide more favorable sites for LSM heterogeneous nucleation. By decreasing the weight ratio of shell precursor to core decreases shell thickness, and reduces the number of homogeneously nucleated LSM nanoparticles, and thereby increases core−shell yield. Increasing the amount of molten salt solvent relative to precursors decreases supersaturation in the melt and results in less uniform, and isolated shell deposition on the cores. The synthesized heterostructred nanoparticles have been functionalized into electrodes for solid oxide fuel cells and electrolysis cells. Symmetrical cells fabricated from baseline LSCF electrodes are compared with symmetrical cells fabricated from the molten salt-synthesized heterostructred electrodes. The heterostructured electrodes are shown to have significantly lower polarization resistance compared to baseline LSCF electrodes, showing the promise of the molten salt process to achieve heterostructured electrodes with substantially reduced polarization resistance.
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Bu, Wenbo, and Jianlin Shi. "Characterization of Highly Luminescent LaPO4:Eu3+/LaPO4 One-Dimensional Core/Shell Heterostructures." Journal of Nanoscience and Nanotechnology 8, no. 3 (March 1, 2008): 1266–71. http://dx.doi.org/10.1166/jnn.2008.18181.

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Highly luminescent LaPO4:Eu3+/LaPO4 one-dimensional (1D) core/shell heterostructures were successfully synthesized by a mild and simple self-aggregation process under refluxing or hydrothermal conditions. The resulting 1D core/shell heterostructures were characterized using a variety of techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) to demonstrate successful coating by the crystalline LaPO4. In addition, a possible formation mechanism for this core/shell heterostructure was proposed. Finally, the photoluminescence property of the LaPO4:Eu3+/LaPO4 1D core/shell heterostructures was investigated in detail, which illustrates that the core/shell heterostructures remarkably increase the luminescence efficiency because the LaPO4 shells effectively eliminate surface trap-states and suppress the energy quenching in the energy-transfer processes.
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Ünlü, Hilmi. "A thermoelastic model for strain effects on bandgaps and band offsets in heterostructure core/shell quantum dots." European Physical Journal Applied Physics 86, no. 3 (June 2019): 30401. http://dx.doi.org/10.1051/epjap/2019180350.

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A thermoelastic model is proposed to determine elastic strain effects on electronic properties of spherical Type I and Type II heterostructure core/shell quantum dots (QDs) as a function of dimensions of constituent semiconductors at any temperature. Proposed model takes into account the difference between lattice constants, linear expansion coefficients and anisotropy of elastic moduli (Young's modulus and Poisson's ratio) of constituent semiconductors, respectively. In analogous to lattice mismatch, we introduce so called the elastic anisotropy mismatch in heterostructures. Compressive strain acting on core (shell) side of heterointerfaces in CdSe/CdS, CdSe/ZnS, and ZnSe/ZnS QDs increases (decreases) as shell diameter is increased, which causes increase (decrease) in core bandgap as sell (core) diameter is increased in these nanostructures. Furthermore, there is a parabolic increase in conduction band offsets and core bandgaps in CdSe/CdS, CdSe/ZnS, and ZnSe/ZnS QDs and decrease in conduction band offset and core bandgap of ZnSe/CdS QD as core (shell) diameter increases for fixed shell (core) diameter. Comparison shows that using isotropic elastic moduli in determining band offsets and core band gaps gives better agreement with experiment than anisotropic elastic moduli for core bandgaps of CdSe/CdS, CdSe/ZnS, ZnSe/ZnS, and ZnSe/CdS core/shell QDs. Furthermore, we also show that the strain-modified two band effective mass approximation can be used to determine band offsets by using measured core band gaps in core/shell heterostructure QDs with Type II interface band alignment. Excellent agreement between predicted and measured core bandgaps in CdSe and ZnSe based core/shell QDs suggests that proposed model can be a good design tool for process simulation of core/shell heterostructure QDs.
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Chopra, Nitin, Yuan Li, and Kuldeep Kumar. "Cobalt oxide-tungsten oxide nanowire heterostructures: Fabrication and characterization." MRS Proceedings 1675 (2014): 191–96. http://dx.doi.org/10.1557/opl.2014.863.

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ABSTRACTNanowire heterostructures comprised of cobalt oxide and tungsten oxide were fabricated in a core/shell configuration. This was achieved by sputter coating tungsten oxide shells on standing cobalt oxide nanowires on a substrate. To ensure the polycrystallinity of tungsten oxide shell, the nanowire heterostructures were subjected to post-sputtering annealing process. The cobalt oxide nanowires for this study were grown employing a thermal method via vapor-solid growth mechanism. The crystal structures, morphologies, dimensions, and phases at various growth stages of nanowire heterostructures were studied using high resolution electron microscopy, energy dispersive spectroscopy, and X-ray diffraction methods. The interfaces of these nanowire heterostructures were also studied and showed variation in the lattice spacing across the heterostructure diameter. Results indicated that the cobalt oxide nanowires survived multiple processing steps and resulted in stable heterostructure configurations. The investigation shows, for the first time, a dry processing route for the formation of such novel nanowire heterostructures.
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Wang, Xuejing, Yung-Chen Lin, Chia-Tse Tai, Seok Woo Lee, Tzu-Ming Lu, Sun Hae Ra Shin, Sadhvikas J. Addamane, et al. "Formation of tubular conduction channel in a SiGe(P)/Si core/shell nanowire heterostructure." APL Materials 10, no. 11 (November 1, 2022): 111108. http://dx.doi.org/10.1063/5.0119654.

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Realizing a tubular conduction channel within a one-dimensional core–shell nanowire (NW) enables better understanding of quantum phenomena and exploration of electronic device applications. Herein, we report the growth of a SiGe(P)/Si core/shell NW heterostructure using a chemical vapor deposition coupled with vapor–liquid–solid growth mechanism. The entire NW heterostructure behaves as a p-type semiconductor, which demonstrates that the high-density carriers are confined within the 4 nm-thick Si shell and form a tubular conduction channel. These findings are confirmed by both calculations and the gate-dependent current–voltage ( I d– V g) characteristics. Atomic resolution microscopic analyses suggest a coherent epitaxial core/shell interface where strain is released by forming dislocations along the axial direction of the NW heterostructure. Additional surface passivation achieved via growing a SiGe(P)/Si/SiGe core/multishell NW heterostructure suggests potential strategies to enhance the tubular carrier density, which could be further modified by improving multishell crystallinity and structural design.
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Han, Delong, Wenlei Tang, Naizhang Sun, Han Ye, Hongyu Chai, and Mingchao Wang. "Shape and Composition Evolution in an Alloy Core–Shell Nanowire Heterostructure Induced by Adatom Diffusion." Nanomaterials 13, no. 11 (May 25, 2023): 1732. http://dx.doi.org/10.3390/nano13111732.

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A core–shell nanowire heterostructure is an important building block for nanowire-based optoelectronic devices. In this paper, the shape and composition evolution induced by adatom diffusion is investigated by constructing a growth model for alloy core–shell nanowire heterostructures, taking diffusion, adsorption, desorption and incorporation of adatoms into consideration. With moving boundaries accounting for sidewall growth, the transient diffusion equations are numerically solved by the finite element method. The adatom diffusions introduce the position-dependent and time-dependent adatom concentrations of components A and B. The newly grown alloy nanowire shell depends on the incorporation rates, resulting in both shape and composition evolution during growth. The results show that the morphology of nanowire shell strongly depends on the flux impingement angle. With the increase in this impingement angle, the position of the largest shell thickness on sidewall moves down to the bottom of nanowire and meanwhile, the contact angle between shell and substrate increases to an obtuse angle. Coupled with the shell shapes, the composition profiles are shown as non-uniform along both the nanowire and the shell growth directions, which can be attributed to the adatom diffusion of components A and B. The impacts of parameters on the shape and composition evolution are systematically investigated, including diffusion length, adatom lifetime and corresponding ratios between components. This kinetic model is expected to interpret the contribution of adatom diffusion in growing alloy group-IV and group III-V core–shell nanowire heterostructures.
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Meier, Johanna, and Gerd Bacher. "Progress and Challenges of InGaN/GaN-Based Core–Shell Microrod LEDs." Materials 15, no. 5 (February 22, 2022): 1626. http://dx.doi.org/10.3390/ma15051626.

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LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while simultaneously increasing the light-emitting area per substrate size. Despite those promises, microrods have still not replaced planar devices. In this review, we discuss the progress in device processing and analysis of microrod LEDs and emphasize the perspectives related to the 3D device architecture from an applications point of view.
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Babu, Bathula, Shaik Gouse Peera, and Kisoo Yoo. "Fabrication of ZnWO4-SnO2 Core–Shell Nanorods for Enhanced Solar Light-Driven Photoelectrochemical Performance." Inorganics 11, no. 5 (May 15, 2023): 213. http://dx.doi.org/10.3390/inorganics11050213.

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This article describes the effective synthesis of colloidal SnO2 quantum dots and ZnWO4 nanorods using wet chemical synthesis and hydrothermal synthesis, respectively. The resulting ZnWO4-SnO2 core–shell nanorod heterostructure is then made, and its structural, optical, and morphological properties are assessed using XRD, SEM, TEM, and DRS. The heterojunction’s structural confinement increases the exposure of its reactive sites, and its electronic confinement promotes its redox activity. The heterostructure subsequently exhibits a smaller bandgap and better light-harvesting capabilities, resulting in increased photoelectrochemical performance. The heterostructure of core–shell nanorods shows promise for usage in a range of optoelectronic devices and effective solar energy conversion.
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Lv, Yuepeng, Sibin Duan, Yuchen Zhu, Peng Yin, and Rongming Wang. "Enhanced OER Performances of Au@NiCo2S4 Core-Shell Heterostructure." Nanomaterials 10, no. 4 (March 27, 2020): 611. http://dx.doi.org/10.3390/nano10040611.

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Transition metal sulfides have attracted a lot of attention as potential oxygen evolution reaction (OER) catalysts. Bimetallic sulfide possesses superior physicochemical properties due to the synergistic effect between bimetallic cations. By introducing a metal-semiconductor interface, the physicochemical properties of transition metal sulfide can be further improved. Using the solvothermal method, Au@NiCo2S4 core-shell heterostructure nanoparticles (NPs) and bare NiCo2S4 NPs were prepared. The measurement of the OER catalytic performance showed that the catalytic activity of Au@NiCo2S4 core-shell heterostructure was enhanced compared to bare NiCo2S4 NPs. At the current density of 10 mA cm−2, the overpotential of Au@NiCo2S4 (299 mV) is lower than that of bare NiCo2S4 (312 mV). The Tafel slope of Au@NiCo2S4 (44.5 mV dec−1) was reduced compared to that of bare NiCo2S4 (49.1 mV dec−1), indicating its faster reaction kinetics. Detailed analysis of its electronic structure, chemical state, and electrochemical impedance indicates that the enhanced OER catalytic performances of bare Au@NiCo2S4 core-shell NPs were a result of its increased proportion of high-valance Ni/Co cations, and its increased electronic conductivity. This work provides a feasible method to improve OER catalytic performance by constructing a metal-semiconductor core-shell heterostructure.
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Chen, Shaohua, Xiaoli Zhao, Fazhi Xie, Zhi Tang, and Xiufang Wang. "Efficient charge separation between ZnIn2S4 nanoparticles and polyaniline nanorods for nitrogen photofixation." New Journal of Chemistry 44, no. 18 (2020): 7350–56. http://dx.doi.org/10.1039/d0nj01102a.

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Novel core–shell polyaniline@ZnIn2S4 core–shell heterostructure photocatalysts have been prepared using a simple synthesis process, and they exhibit superior performances of photocatalytic N2 reduction to NH3 in an atmospheric environment.
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Dissertations / Theses on the topic "Core-shell Heterostructure"

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Walsh, T. M. "Theoretical characterisation of spheroidal PbSe/PbS core/shell colloidal quantum dot heterostructures." Thesis, University of Salford, 2016. http://usir.salford.ac.uk/41075/.

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Nanocrystal quantum dots (NQDs) show great promise in the advancement of the field of photovoltaics. While the maximum efficiency of conventional solar cell (SC) devices is limited to ∼ 31% (Shockley-Queisser limit), devices based on NQDs may attain a maximal thermodynamic efficiency of 42% through the exploitation of multiple exciton generation (MEG). In this process, several electron- hole pairs are created by the absorption of a single high energy photon, as opposed to the single excitons created in conventional solar cell devices. IV-VI semiconductor nanocrystals (PbS, PbSe) are of particular interest as candidates for the exploitation of MEG due to the narrow band gap, high confinement energies, and long radiative carrier lifetimes observed in these systems. In order to realise the full potential of MEG devices, full characterisation of the optoelectronic properties of the underlying nanoparticles is desirable. While the size-dependent properties of NQDs are well understood, the effects of NQD shape are less so. This thesis investigates the effect of ellipticity on the optoelectronic properties associated with spheroidal NQDs. To this end, a four-band, anisotropic, and radially variant k · p system Hamiltonian is expanded in a planewave basis in order to calculate single-particle eigenenergies and eigenfunctions of colloidal PbSe/PbS core/shell heterogeneous NQDs of varying ellipticity. Many-body effects are accounted for via a full configuration interaction (CI) Hamiltonian, the basis of which is comprised of the single-particle states. Exci- tonic and bi-excitonic corrections are then found by mixing of the basis states. In this manner, such diverse electronic and optical properties as quasi-particle binding energies, momentum matrix elements, and charge carrier lifetimes, both radiative and non-radiative, may be predicted.
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Migas, Jeremiah. "A PHOTOCATALYTIC INVESTIGATION OF CORE-SHELL AND HIERARCHICAL Zn-Ti-O/ZnO HETEROSTRUCTURES PRODUCED BY HYBRID HYDROTHERMAL GROWTH AND SPUTTERING TECHNIQUES." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/824.

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With an increasing demand for alternative clean energy solutions, much effort is being invested in the progression of nanoscale semiconductor materials in hopes of better harnessing solar energy. ZnO and TiO2 remain the most prominent photocatalytically active materials. This thesis reports on a comparison between nanoscale core-shell and hierarchical Zn-Ti-O/ZnO heterostructures. After a seed layer thickness optimization, hydrothermally grown ZnO nanorods were coated with mixed concentrations of Ti and Zn within an oxygen rich sputtering environment at two distinct temperature zones. Core-shell structures resulted from low temperature (23°C) depositions while hierarchical branch structures grew at high temperature (800°C). Excluding deposition temperature and the strategic variation of Zn and Ti gun power, every fabrication process remained identical between the two resultant heterostructure groups. Amongst the variety of samples produced, one from each heterostructure group proved notably similar in structural dimension, composition, and crystallization, yet demonstrated distinct differences in photoluminescence and dye degradation via UV-visible light spectroscopy. While photoluminescence results indicated core-shell heterostructure more photocatalytically promising, hierarchical heterostructure prevailed as the more powerful photocatalyst. Increased surface area due to hierarchical branching in conjunction with enhanced light exposure was believed responsible for the improved photocatalytic effectiveness.
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Connors, Benjamin James. "Simulation of current crowding mitigation in GaN core-shell nanowire led designs." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41206.

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Core-shell nanowire LEDs are light emitting devices which, due to a high aspect ratio, have low substrate sensitivity, allowing the possibility of low defect density GaN light emitting diodes. Current growth techniques and physical non-idealities make the production of high conductivity p-type GaN for the shell region of these devices difficult. Due to the structure of core-shell nanowires and the difference in conductivity between ntype and p-type GaN, the full junction area of a core-shell nanowire is not used efficiently. To address this problem, a series of possible doping profiles are applied to the core of a simulated device to determine effects on current crowding and overall device efficiency. With a simplified model it is shown that current crowding has a possible dependence on the doping in the core in regions other than those directly in contact with the shell. The device efficiency is found to be improved through the use of non-constant doping profiles in the core region with particularly large efficiency increases related to profiles which modify portions of the core not in contact with the shell
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Adam, Adeline. "étude du couplage élastique au sein d'hétérostructures cœur-coquille à base d'analogues du bleu de Prusse." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX076/document.

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Le contrôle optique des propriétés physiques d’un matériau suscite l’intérêt des scientifiques pour des enjeux aussi bien fondamentaux qu’appliqués. L’axe de recherche original que nous avons développé dans le cadre de ce travail de thèse visait à la réalisation et l’étude d’hétérostructures moléculaires photo-magnétiques dans des gammes de température susceptibles d’applications. L’approche proposée consistait à élaborer des hétérostructures de type multiferroïque constituées de deux phases, l’une piézomagnétique et l’autre photo-strictive. L’idée était d’optimiser le couplage, d’origine élastique, entre ces propriétés pour permettre l’observation d’effets photo-magnétiques à des températures plus élevées que celles rapportées pour les matériaux monophasés. La couche photo-strictive peut se déformer sous irradiation lumineuse, générant des contraintes biaxiales dans la couche magnétique. Si celle-ci présente une forte réponse piézomagnétique, son aimantation peut être fortement modifiée, notamment au voisinage du point de Curie, allant jusqu’à un éventuel décalage de la température critique sous contrainte. Les composés moléculaires analogues du Bleu de Prusse, de formule générique AxM[M’(CN)6]y . zH2O (où A est un alcalin et M,M’ des métaux de transition), semblaient particulièrement adaptés à l’élaboration de telles hétérostructures. Nous avons utilisé le composé Rb0,5Co[Fe(CN)6]0,8 . zH2O pour la phase photo-strictive, au coeur, et Rb0,2Ni[Cr(CN)6]0,7 . z’H2O ou K0,2Ni[Cr(CN)6]0,7 . z’H2O pour la phase magnétique, en coquille. Ces deux phases présentent un désaccord paramétrique de 5,3%.L’objectif principal de ce travail de thèse était de comprendre et de contrôler le couplage élastique entre le cœur et la coquille. Nous avons ainsi dans un premier temps mis en évidence l’existence de ce couplage, la présence de la coquille modifiant les propriétés de photo-commutation du cœur et la déformation du réseau cristallin du cœur étant partiellement transmise à la coquille, induisant des modifications structurales et magnétiques de la coquille. Nous nous sommes dans un second temps intéressés à différents paramètres pouvant influence le couplage. D’abord en étudiant des paramètres géométriques, en faisant varier la taille des particules de cœur, l’épaisseur de la coquille et la microstructure de la coquille. Nous avons à cette occasion mis en évidence les facteurs régissant la croissance des particules de cœur et de la coquille. Ces études ont révélé que le rapport volumique entre le cœur et la coquille contrôlait la qualité du couplage, et que des modifications de la microstructure avait une influence à la fois sur les propriétés de photo-commutation du cœur, mais aussi sur la réponse de la coquille. Enfin, nous avons étudié des coquilles de nature chimique différente pour changer le désaccord paramétrique entre le cœur et la coquille. Il en ressort qu’en diminuant le désaccord, on améliore le couplage, mais cela se traduit notamment par une rétroaction de la coquille plus forte. Si cette rétroaction devient trop importante, le réseau du cœur ne peut plus se déformer. Il s’agit donc de trouver un compromis entre force du couplage et force de la rétroaction de la coquille. Finalement, nous avons mis en évidence le fait que l’on ne peut pas simplement associer l’effet de la coquille à un effet de pression hydrostatique, mais que le couplage des réseaux cristallins joue un rôle important dans la synergie entre les deux phases
The optical control of the physical properties of a material has drawn considerable attention during the past few years for a fundamental point of view and for applications. The originality of the project developed during this thesis was based on the synthesis and the study of photo-magnetic heterostructures in a temperature range convenient for applications. The approach consisted of developing multiferroic-like heterostructures that associate a piezomagnetic phase and a photo-strictive phase. The idea was to exploit the coupling of elastic origin between these properties, to allow the observation of photo-magnetic effects at temperatures higher than those reported for single-phase materials. The photo-strictive phase can deform under light irradiation, generating biaxial strain in the magnetic phase. If the piezomagnetic response of the latter is high enough, its magnetization could be modulated, especially at the vicinity of the Curie temperature, with a possible shift of the critical temperature under stress. In this project, we focused on molecular solids based on polycyanometallates, namely Prussian blue analogues, whose generic formula is AxM[M’(CN)6]y . zH2O (where A is an alkali metal and M,M transition metals). We used the compound Rb0,5Co[Fe(CN)6]0,8 . zH2O for the photo-strictive phase and Rb0,2Ni[Cr(CN)6]0,7 . z’H2O or K0,2Ni[Cr(CN)6]0,7 . z’H2O for the magnetic phase. These two phases have a lattice mismatch of 5.3%The main objective of this work was to understand and to control the elastic coupling between the core and the shell. We first highlighted the existence of this coupling, the presence of the shell changing the photo-switching properties of the core, and the deformation of the crystalline lattice of the core inducing structural and magnetic modifications in the shell. Then, we focused on the study of different parameters which can have an impact on the behavior of the heterostructures under light irradiation. We showed that the volumic ratio between the core and the shell is a key factor to control the efficiency of the coupling. The microstructure of the shell can also play an important role, but is not as well understood. In the end, we studied other Prussian blue analogs shells in order to change the lattice mismatch between the core and the shell. We could evidence that by reducing the lattice mismatch we tend to increase the coupling, but if this coupling is to strong, the retroaction of the shell hinders completely the dilatation of the core lattice. The idea is also to find a compromise between the strength of the coupling and the strength of the shell retroaction. In the end, we proved that we cannot associate the effect of the shell to an hydrostatic pressure, but that the coupling of the crystalline lattices play an important role in the synergy between the two phases
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Cossuet, Thomas. "Problématique de la polarité dans les nanofils de ZnO localisés, et hétérostructures reliées pour l’opto-électronique." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI086/document.

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Le développement d’architectures nanostructurées originales composées de matériaux abondants et non-toxiques fait l’objet d’un fort intérêt de la communauté scientifique pour la fabrication de dispositifs fonctionnels efficaces et à bas coût suivant des méthodes d’élaborations faciles à mettre en œuvre. Les réseaux de nanofils de ZnO élaborés par dépôt en bain chimique sont, à ce titre, extrêmement prometteurs. L’étude des propriétés de ces réseaux de nanofils et leur intégration efficace au sein de dispositifs nécessitent toutefois un contrôle avancé de leurs propriétés structurales et physiques, notamment en terme de polarité, à l’aide de techniques de lithographies avancées.Le dépôt en bain chimique des nanofils de ZnO est d’abord effectué sur des monocristaux de ZnO de polarité O et Zn préparés par lithographie assistée par faisceau d’électrons. Par cette approche de croissance localisée, un effet significatif de la polarité des nanofils de ZnO est mis en évidence sur le mécanisme de croissance des nanofils, ainsi que sur leurs propriétés électriques et optiques. La possibilité de former des nanofils de ZnO sur des monocristaux de ZnO semipolaires nous a de plus permis d’affiner la compréhension de leurs mécanismes de croissance sur les couches d’amorces polycristallines de ZnO. Par la suite, le dépôt des nanofils de ZnO en bain chimique est développé sur des couches d’amorces polycristallines de ZnO préparés à l’aide de la lithographie assistée par nano-impression. Suivant cette approche, des réseaux de nanofils de ZnO localisés sont formées sur de grandes surfaces, ce qui permet d’envisager leur intégration future au sein de dispositifs fonctionnels.Les nanofils de ZnO sont ensuite combinés avec des coquilles semiconductrices de type p par des méthodes de dépôt chimique en phase liquide ou en phase vapeur afin de fabriquer des hétérostructures cœurs-coquilles originales. Le dépôt de couches successives par adsorption et réaction (SILAR) d’une coquille absorbante de SnS de phase cubique est optimisé sur des nanofils de ZnO recouverts d’une fine couche protectrice de TiO2, ouvrant la voie à la fabrication de cellules solaires à absorbeur extrêmement mince. Enfin, un photo-détecteur UV autoalimenté prometteur, présentant d’excellentes performances en termes de réponse spectrale et de temps de réponse, est réalisé par le dépôt chimique en phase vapeur d’une coquille de CuCrO2 sur les nanofils de ZnO
Over the past decade, the development of novel nanostructured architectures has raised increasing interest within the scientific community in order to meet the demand for low-cost and efficient functional devices composed of abundant and non-toxic materials. A promising path is to use ZnO nanowires grown by chemical bath deposition as building blocks for these next generation functional devices. However, the precise control of the ZnO nanowires structural uniformity and the investigation of their physical properties, particularly in terms of polarity, remain key technological challenges for their efficient integration into functional devices.During this PhD, the chemical bath deposition of ZnO nanowires is combined with electron beam lithography prepared ZnO single crystal substrates of O- and Zn-polarity following the selective area growth approach. The significant effects of polarity on the growth mechanism of ZnO nanowires, as well as on their electrical and optical properties, are highlighted by precisely investigating the resulting well-ordered O- and Zn-polar ZnO nanowire arrays. An alternative nano-imprint lithography technique is subsequently used to grow well-ordered ZnO nanowire arrays over large areas on various polycrystalline ZnO seed layers, thus paving the way for their future integration into devices. We also demonstrate the possibility to form ZnO nanowires by chemical bath deposition on original semipolar ZnO single crystal substrates. These findings allowed a comprehensive understanding of the nucleation and growth mechanisms of ZnO nanowires on polycrystalline ZnO seed layers.In a device perspective, the ZnO nanowires are subsequently combined with p type semiconducting shells by liquid and vapor chemical deposition techniques to form original core-shell heterostructures. The formation of a cubic phase SnS absorbing shell is optimized by the successive ionic layer adsorption and reaction (SILAR) process on ZnO nanowire arrays coated with a thin protective TiO2 shell, which pave the way for their integration into extremely thin absorber solar cells. A self-powered UV photo-detector with fast response and state of the art performances is also achieved by the chemical vapor deposition of a CuCrO2 shell on ZnO nanowire arrays
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Mouafo, Notemgnou Louis Donald. "Two dimensional materials, nanoparticles and their heterostructures for nanoelectronics and spintronics." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE002/document.

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Cette thèse porte sur l’étude du transport de charge et de spin dans les nanostructures 0D, 2D et les hétérostructures 2D-0D de Van der Waals (h-VdW). Les nanocristaux pérovskite de La0.67Sr0.33MnO3 ont révélé des magnétorésistances (MR) exceptionnelles à basse température résultant de l’aimantation de leur coquille indépendamment du coeur ferromagnétique. Les transistors à effet de champ à base de MoSe2 ont permis d’élucider les mécanismes d’injection de charge à l’interface metal/semiconducteur 2D. Une méthode de fabrication des h-VdW adaptés à l’électronique à un électron est rapportée et basée sur la croissance d’amas d’Al auto-organisés à la surface du graphene et du MoS2. La transparence des matériaux 2D au champ électrique permet de moduler efficacement l’état électrique des amas par la tension de grille arrière donnant lieu aux fonctionnalités de logique à un électron. Les dispositifs à base de graphene présentent des MR attribuées aux effets magnéto-Coulomb anisotropiques
This thesis investigates the charge and spin transport processes in 0D, 2D nanostructures and 2D-0D Van der Waals heterostructures (VdWh). The La0.67Sr0.33MnO3 perovskite nanocrystals reveal exceptional magnetoresistances (MR) at low temperature driven by their paramagnetic shell magnetization independently of their ferromagnetic core. A detailed study of MoSe2 field effect transistors enables to elucidate a complete map of the charge injection mechanisms at the metal/MoSe2 interface. An alternative approach is reported for fabricating 2D-0D VdWh suitable for single electron electronics involving the growth of self-assembled Al nanoclusters over the graphene and MoS2 surfaces. The transparency the 2D materials to the vertical electric field enables efficient modulation of the electric state of the supported Al clusters resulting to single electron logic functionalities. The devices consisting of graphene exhibit MR attributed to the magneto-Coulomb effect
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Gomes, Umesh Prasad. "Catalyst-assisted and catalyst-free growth of III-V semiconductor nanowires." Doctoral thesis, Scuola Normale Superiore, 2017. http://hdl.handle.net/11384/85884.

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The aim of this thesis is to understand the dynamics of the nucleation and growth of III-V semiconductor nanowires and associated heterostructures grown by chemical beam epitaxy. These nanowires represent well-controlled and high quality materials suitable for both fundamental physics and applications in optical and electronic devices. The first part of the thesis investigates growth recipes to obtain Au-catalyzed InAs NWs with controlled morphology. Good control of NW length and diameter distributions has been achieved by a systematic study of two different Au deposition techniques: Au thin film deposition and colloidal dispersion. Triggered by the issues of Au contamination and CMOS compatibility, the second part of the thesis is dedicated to the investigation of the nucleation and growth mechanisms of Au-free InAs NWs on Si (111) substrates. A thorough analysis of the silicon substrate preparation is conducted and an optimized silicon surface for the nucleation of Au-free nanowires is identified. We show that the silicon surface can be modified by in situ and ex situ parameters allowing us to control the density of NWs. Growth conditions were established for growing InAs NWs either by catalyst-free or self-catalyzed mechanisms on Si (111). The catalyst-free growth proceeds in the vapor-solid growth mechanism without the use of any catalyst particle while the self-catalyzed growth proceeds in the vapor-liquid-solid mechanism involving a liquid In droplet. Growth models are proposed in order to interpret the experimental findings. The third part of the thesis concerns the growth of axial and radial (core-shell) heterostructured NWs. Nanowire heterostructures combining either highly lattice mismatched materials (GaAs and InAs) or almost lattice matched materials (InAs and GaSb) are investigated. GaAs/InAs and InAs/GaAs axial heterostructures are grown by Au-catalyzed method. Here, it is demonstrated that the catalyst composition, rather than other growth parameters, as postulated so far, controls the growth mode and the resulting NW morphology. We have also explored the growth of core-shell InAs/GaSb heterostructures by catalyst-free mechanism. The morphology and structural properties of InAs/GaSb core-shell heterostructures are optimized to fabricate Esaki tunnel diodes exploiting their broken-gap band alignment.
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Lee, Yan-Tsuo, and 李彥佐. "Synthesis and Characterization of Core-ZnO/Shell-MgZnO Heterostructure Nanorods." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/f7h5p7.

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碩士
國立臺北科技大學
光電工程系研究所
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The formation of heterostrucure in nanorods is essential for their potential applications in nanoelectronic and photonic devices. Here we demonstrate that vertically well-aligned ZnO nanorods and ZnO/MgZnO core-shell nanorods can be successfully synthesized via catalyst-free vapor phase transport combined with pulsed laser deposition (PLD) method. The thesis consists of two parts. First, the vertically well-aligned ZnO nanorods were grown on a PLD-predeposited ZnO thin film via a simple thermal evaporation and vapor transport process. These ZnO nanorods were quite uniform with a diameter of ~27 nm and length of ~1 μm. Room-temperature photoluminescence spectra of the samples showed only a strong band-edge emission, indicating the high crystalline quality. The well-aligned ZnO nanorods were used as a template for the synthesis of nanorod heterostructures. In the second part, the vertically well-aligned ZnO/MgZnO core-shell structures of the nanorods were synthesized by PLD of MgZnO onto the ZnO nanorod template. The core-shell heterostructure nanorods were examined by high-resolution transmission electron microscopy measurements. The optical properties of the heterostructure nanorods were analyzed by photoluminescence. The HRTEM images and the corresponding FFT patterns of the nanorods implied that the core/shell is wurtzite structured ZnO/MgZnO with well-defined epitaxial relationship. The positions of the MgxZn1-xO shells, obtained by pused laser ablating MgyZn1-yO targets with y=0.0909 and 0.25, were determained by the Vegard’s law to be x=0.14 and 0.30, respectively. Room-temperature PL spectrum from the ZnO/MgxZn1-xO core-shell nanorods exhibits strong emissions from ZnO core (located at 3.298eV) and MgxZn1-xO shell (located at 3.539eV for x=0.14 and 3.935eV for x=0.30). The core/shell relative emission intensity can be controlled by the shell thickness.
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HSU, NAI-CHIEH, and 徐廼杰. "Enhancement on field emission properties of nanowires using ZnO-Zn core-shell heterostructure." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/49yavd.

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Dillen, David Carl. "Confined electron systems in Si-Ge nanowire heterostructures." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4360.

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Semiconductor nanowire field-effect transistors (NWFET) have been recognized as a possible alternative to silicon-based CMOS technology as traditional scaling limits are neared. The core-shell nanowire structure, in particular, also allows for the enhancement of carrier mobility through radial band engineering. In this thesis, we have evaluated the possibility of electron confinement in strained Si-Si1-xGex core-shell nanowire heterostructures. Cylindrical strain distribution was calculated analytically for structures of various dimensions and shell compositions. The strain-induced conduction band edge shift of each region was found using k•p theory coupled with a coordinate system shift to account for strain. A positive conduction band offset of up to 200 meV was found for a Si-Si0.2Ge0.8 structure. We have also designed and characterized a modulation doping scheme for p-type, Ge-SiGe core-shell NWFETs. Finite element simulations of hole density versus radial position were done for different combinations of dopant position and concentration. Three modulation doped nanowire samples, each with a different boron doping density in the shell, were grown using a combined vapor-liquid-solid and chemical vapor deposition process. Low temperature current-voltage measurements of bottom- and top-gate samples indicate that hole mobility is limited by the proximity of charged impurities.
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Book chapters on the topic "Core-shell Heterostructure"

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Buscaglia, Vincenzo, and Maria Teresa Buscaglia. "Core-Shell Heterostructures: From Particle Synthesis to Bulk Dielectric, Ferroelectric, and Multiferroic Composite Materials." In Nanoscale Ferroelectrics and Multiferroics, 72–99. Chichester, UK: John Wiley & Sons, Ltd, 2016. http://dx.doi.org/10.1002/9781118935743.ch3.

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Chen, Minghua, Nianbo Zhang, Jiawei Zhang, and Yu Li. "Enhancing Specific Capacitance and Structural Durability of VO2 Through Rationally Constructed Core-Shell Heterostructures." In The Proceedings of the 5th International Conference on Energy Storage and Intelligent Vehicles (ICEIV 2022), 1128–36. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1027-4_117.

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Shi, Wenwu, and Nitin Chopra. "Magnetically-Driven Release Media Comprising of Carbon Nanotube-Nickel/Nickel Oxide Core/Shell Nanoparticle Heterostructures Incorporated in Polyvinyl Alcohol." In Ceramic Transactions Series, 107–13. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118144602.ch11.

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Eymery, J., and D. Le Si Dang. "Growth of GaN-based nanorod heterostructures (core-shell) for optoelectronics and their nanocharacterization." In Modeling, Characterization, and Production of Nanomaterials, 323–35. Elsevier, 2015. http://dx.doi.org/10.1016/b978-1-78242-228-0.00012-0.

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Lifshitz, Efrat, Georgy I., Roman Vaxenburg, Diana Yanover, Anna Brusilovski, Jenya Tilchin, and Aldona Sashchiuk. "Temperature-Dependent Optical Properties of Colloidal IV-VI Quantum Dots, Composed of Core/Shell Heterostructures with Alloy Components." In Fingerprints in the Optical and Transport Properties of Quantum Dots. InTech, 2012. http://dx.doi.org/10.5772/35048.

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Conference papers on the topic "Core-shell Heterostructure"

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Ünlü, Hilmi. "Modelling of CdSe/CdZnS and ZnSe/CdZnS binary/ternary heterostructure core/shell quantum dots." In TURKISH PHYSICAL SOCIETY 33RD INTERNATIONAL PHYSICS CONGRESS (TPS33). Author(s), 2018. http://dx.doi.org/10.1063/1.5025975.

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Gollner, Claudia, Rokas Jutas, Dominik Kreil, Dmitry N. Dirin, Simon C. Boehme, Andrius Baltuška, Maksym V. Kovalenko, and Audrius Pugžlys. "Direct THz field driven electro-absorption modulation in heterostructure quantum dots." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/up.2022.tu5a.4.

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We report on electro-absorption switching in colloidal CdSe/CdS core/shell quantum dots, gated by intense THz pulses, without field enhancing structures, and suggest a route to optimize electro-absorption modulators with respect to the energy band alignment of the heterostructure material.
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Karim, M. Rezaul, and Hilmi Ünlü. "Temperature and strain effects on core bandgap and diameter of bare CdSe core and CdSe/ZnS heterostructure core/shell quantum dots." In TURKISH PHYSICAL SOCIETY 33RD INTERNATIONAL PHYSICS CONGRESS (TPS33). Author(s), 2018. http://dx.doi.org/10.1063/1.5025976.

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Didarataee, S., A. Khodadadi, M. Mortazavi, and F. Mousavi. "Undoped and Fe-doped core/shell ZnS@ZnO heterostructure for photocatalytic water splitting hydrogen evolution." In 2021 IEEE 21st International Conference on Nanotechnology (NANO). IEEE, 2021. http://dx.doi.org/10.1109/nano51122.2021.9514347.

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Gollner, Claudia, Rokas Jutas, Dominik Kreil, Dmitry N. Dirin, Simon C. Boehme, Andrius Baltuška, Maksym V. Kovalenko, and Audrius Pugžlys. "Dependence of a direct THz driven Stark effect on the energy band alignment in heterostructure Quantum Dots." In CLEO: QELS_Fundamental Science. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_qels.2022.fth4a.2.

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We report on direct ultrafast electro-absorption switching in colloidal CdSe/CdS core/shell quantum dots driven by intense THz pulses without a field enhancing structure, and suggest a route to optimize electro-absorption modulators with respect to the energy band alignment of the heterostructure material.
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Antonello, Alessandro, Massimo Guglielmi, Valentina Bello, Giovanni Mattei, and Alessandro Martucci. "Synthesis and tailoring of CdSe core@shell heterostructures for optical applications." In SPIE OPTO, edited by Jean E. Broquin and Gualtiero Nunzi Conti. SPIE, 2011. http://dx.doi.org/10.1117/12.873678.

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Yang, Ronggui, Gang Chen, and Mildred S. Dresselhaus. "Thermal Conductivity of Core-Shell Nanostructures: From Nanowires to Nanocomposites." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72198.

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Core-shell heterostructures could potentially become the building blocks of nanotechnology for electronic and optoelectronic applications. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management such devices. In the mean time, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, a generic model is established to study phonon transport in core-shell nanowire structures in the longitudinal direction using the phonon Boltzmann equation. The model can be used to simulate a variety of nanostructures, including nanowires and nanocomposites by changing some of the input parameters. We first report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core - germanium shell and tubular silicon nanowires. When the scattering at the outer shell surface in the generic model is assumed to be totally specular, the core-shell nanostructure resembles a simulation unit cell of periodic two-dimensional (2-D) nanocomposites. Thermal conductivity of nanowire composites and cylindrical nanoporous material in longitudinal direction is thus predicted as a function of the size of the nanowires and nanopores, and the volumetric fraction of the constituent materials. Results of this study can be used to direct the development of high efficiency thermoelectric materials.
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Singh, Ashutosh Kumar, and Kalyan Mandal. "High performance supercapacitor electrodes based on metal/metal-oxide core/shell nano-heterostructures." In NANOFORUM 2014. AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4917644.

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Borras, Ana, Manuel Macias-Montero, Angel Barranco, Jose Cotrino, Juan Espinos, and Augustin R. González-Elipe. "Fabrication of heterostructured M@M´Ox Nanorods by low temperature PECVD." In 13th International Conference on Plasma Surface Engineering September 10 - 14, 2012, in Garmisch-Partenkirchen, Germany. Linköping University Electronic Press, 2013. http://dx.doi.org/10.3384/wcc2.47-50.

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In this communication we report on the fabrication of two different heterostructured core@shell 1D materials by low temperature (135 oC) plasma enhanced chemical deposition: Ag@TiO2 and Ag-NPs@ZnO nanorods (NRs). The controlled formation of these heterostructures on processable substrates such as Si wafers, fused silica and ITO is demonstrated. The NRs are studied by SEM, HAADF-STEM, TEM, XRD and in situ XPS in order to fully describe their microstructure and inner structure, eventually proposing a growth mechanism. The first type of nanostructures consists on a silver wire surrounded by a TiO2 shell that grows following the volcano-like mechanism. The Ag-NPs@ZnO nanostructures are formed by supported ZnO nanorods decorated with Ag nanoparticles (NPs). The 3D reconstruction by HAADF-STEM electron tomography reveals that the Ag NPs are distributed along the hollow interior of highly porous ZnO NRs. The aligned Ag-NPs@ZnO-NRs grow by a combination of different factors including geometrical distribution of precursor, plasma sheath and differences in the silver/silver oxide densities. Tuning the deposition angle, Ag-NPs@ZnO-NRs depicting different tilting angles can be homogeneously grown allowing the formation of zig-zag nanostructures. The as prepared surfaces are superhydrophobic with water contact angles higher than 150o. These surfaces turn into superhydrophilic with water contact angles lower than 10º after irradiation under UV light. In the case of the AgNPs@ZnO NRs such modification can be also provoked by irradiation with VIS light. The evolution rate of the wetting angle and its dependence on the light characteristics are related with the nanostructure and the presence of silver embedded within the NRs.
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Nah, Junghyo, K. M. Varahramyan, E. S. Liu, A. Opotowsky, D. Ferrer, S. K. Banerjee, and E. Tutuc. "Growth and electronic properties of Ge-Si x Ge 1-x core-shell nanowire heterostructures." In SPIE NanoScience + Engineering, edited by M. Saif Islam, A. Alec Talin, and Stephen D. Hersee. SPIE, 2009. http://dx.doi.org/10.1117/12.829159.

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Reports on the topic "Core-shell Heterostructure"

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Nakotte, Tom. Engineering of Lead Selenide Quantum Dot Based Devices and Core/Shell Heterostructures. Office of Scientific and Technical Information (OSTI), April 2020. http://dx.doi.org/10.2172/1614831.

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Gopalan, Srikanth, and Ben Levitas. Core-Shell Heterostructures as Functional Materials for Solid Oxide Fuel Cell (SOFC) Electrodes. Office of Scientific and Technical Information (OSTI), June 2022. http://dx.doi.org/10.2172/1872369.

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