Articles de revues : « Shell nanowire »

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Chopra, Nitin, Yuan Li et 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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Lee, Sun Sook, Hyun Jin Kim, Taek-Mo Chung, Young Kuk Lee, Chang Gyoun Kim et Ki-Seok An. « Fabrication of Nanocomposite Based on ZnO Nanowire ». Journal of Nanoscience and Nanotechnology 8, n^o 9 (1 septembre 2008) : 4895–98. http://dx.doi.org/10.1166/jnn.2008.ic80.

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ZnO-NiO core–shell nanowires and Ni-ZnO nanoparticle–nanowire composites have been synthesized by atomic layer deposition (ALD) and H2 thermal reduction, respectively. Grown ZnO nanowires on Si substrates by vapor transport method were used as templates for the growth of NiO layers. In order to prevent interfacial interaction between deposited NiO and ZnO nanowires templates by the reaction at low temperature and to precisely control the thickness of NiO layer, ALD technique was suitably employed to form the ZnO-NiO core–shell nanowires. All surface area of ZnO nanowires was completely and uniformly covered by amorphous NiO layers at low temperature of 130 °C. The Ni-ZnO nanoparticle–nanowire composites were achieved by the thermal reduction of the ZnO-NiO core–shell nanowires at H2 atmosphere. The density of Ni nanoparticles on ZnO nanowires was roughly related to the pre-deposited NiO thickness and the inter-diffusion of Ni into the ZnO nanowire was not observed.

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Son, Kwang-Soo, Dong Hyun Lee, Jae-Woong Choung, Yong Bum Pyun, Won Il Park, Taeseup Song et Ungyu Paik. « Catalyst-free synthesis and cathodoluminescent properties of ZnO nanobranches on Si nanowire backbones ». Journal of Materials Research 23, n^o 12 (décembre 2008) : 3403–8. http://dx.doi.org/10.1557/jmr.2008.0400.

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We report the catalyst-free synthesis of ZnO nanobranches on Si nanowires using metalorganic chemical vapor deposition. The formation of single-crystalline ZnO nanobranches on Si nanowire backbones has been confirmed by lattice resolved transmission electron microscopy. Depending on the growth parameters, especially the growth temperature, the morphology and size of the ZnO nanobranches evolved from nanothorn-shaped (at 350 °C) to nanoneedle-shaped structures (at 500 °C). When the growth temperature was further increased to 800 °C, thin ZnO nanowire branches grew out of the Si nanowire backbones coated with thin ZnO shells, whereas no ZnO branch was formed on bare Si nanowires due to limited nucleation. The growth behavior was further exploited to fabricate ZnO/Si nanowire networks by growing the ZnO nanowires selectively on laterally aligned Si–ZnO core-shell nanowire arrays. In addition, cathodoluminescent properties of ZnO nanobranches on Si nanowire backbones are discussed with respect to position and size.

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VERMA, ASHWANI, BAHNIMAN GHOSH et AKSHAY KUMAR SALIMATH. « EFFECT OF ELECTRIC FIELD, TEMPERATURE AND CORE DIMENSIONS IN III–V COMPOUND CORE–SHELL NANOWIRES ». Nano 09, n^o 04 (juin 2014) : 1450051. http://dx.doi.org/10.1142/s1793292014500519.

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In this paper, we have used semiclassical Monte Carlo method to show the dependence of spin relaxation length in III–V compound semiconductor core–shell nanowires on different parameters such as lateral electric field, temperature and core dimensions. We have reported the simulation results for electric field in the range of 0.5–10 kV/cm, temperature in the range of 77–300 K and core length ranging from 2 nm to 8 nm. The spin relaxation mechanisms used in III–V compound semiconductor core–shell nanowire are D'yakonov–Perel (DP) relaxation and Elliott–Yafet (EY) relaxation. Depending upon the choice of materials for core and shell, nanowire forms two types of band structures. We have used InSb – GaSb core–shell nanowire and InSb – GaAs core–shell nanowire and nanowire formed by swapping the core and shell materials to show all the results.

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Liu, Liqing, Hui Wang, Dehao Wang, Yongtao Li, Xuemin He, Hongguang Zhang et Jianping Shen. « ZnO@TiO2 Core/Shell Nanowire Arrays with Different Thickness of TiO2 Shell for Dye-Sensitized Solar Cells ». Crystals 10, n^o 4 (21 avril 2020) : 325. http://dx.doi.org/10.3390/cryst10040325.

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The ZnO@TiO2 core/shell nanowire arrays with different thicknesses of the TiO2 shell were synthesized, through depositing TiO2 on the ZnO nanowire arrays using the pulsed laser deposition process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that these core/shell nanowires were homogeneously coated with TiO2 nanoparticles with high crystallinity, appearing to be a rather rough surface compared to pure ZnO nanowires. The efficiency of ZnO@TiO2 core/shell structure-based dye-sensitized solar cells (DSSCs) was improved compared with pure ZnO nanowires. This is mainly attributed to the enlarged internal surface area of the core/shell structures, which increases dye adsorption on the anode to improve the light harvest. In addition, the energy barrier which formed at the interface between ZnO and TiO2 promoted the charge separation and suppressed the carrier recombination. Furthermore, the efficiency of DSSCs was further improved by increasing the thickness of the TiO2 shell. This work shows an efficient method to achieve high power conversion efficiency in core/shell nanowire-based DSSCs.

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Shiave, Ali Imran, Ravi Pratap Singh Tomar, Ingrid Padilla Espinosa et Ram Mohan. « Deformation Mechanisms and Dislocations in Nickel–Cobalt Core–Shell Nanowires Under Uniaxial Tensile Loading—A Molecular Dynamics Modeling Analysis ». Advanced Science, Engineering and Medicine 11, n^o 12 (1 décembre 2019) : 1187–201. http://dx.doi.org/10.1166/asem.2019.2478.

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One-Dimensional nanostructures are of great importance due to their unique electrical, magnetic and mechanical properties. Because of the size constraints, it is impractical to obtain and understand their mechanical properties, deformation behavior and associated mechanisms experimentally, while atomistic computational modeling offers a viable approach. Several studies have focused on pure metallic and compound nanowires; however, investigations and data for core–shell nanowires is still very limited. Present work models and analyzes Nickel–Cobalt (Ni–Co) core–shell nanowire systems under uniaxial tensile loading via molecular dynamics (MD) modeling. Present studies and analysis focus on predictive mechanical properties as well as insights on deformation mechanisms and dislocations during uniaxial tensile loading. Further, pure Ni and Co nanowire systems of similar configurations are modeled, and compared to our findings of core–shell nanowire systems. Results indicate that crystal mismatch in the region of core–shell interface have a significant effect, and plays an important role in the deformation process. Evolution of dislocations during uniaxial tensile loading deformation process, following a dislocation extraction analysis are presented and discussed. Further investigations of the core–shell nanowire structures involved a systematic study on the effect of core size on the predicted mechanical properties. Results indicate that the yield strength and Young's modulus indicated a linear increase for nickel shell–cobalt core systems with a Cobalt core for increasing core sizes, while maintaining nearly similar volume, length, and outer diameter of the core–shell nanowire system. Cobalt shell–nickel core nanowire systems with nickel core however was found not to depict any such definitive characteristics.

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Azmy, Ilham, et Jun Wang. « Construction of Hierarchical CuCo2O4-Ni(OH)2 Core-Shell Nanowire Arrays for High-Performance Pseudocapacitors ». Aceh International Journal of Science and Technology 11, n^o 1 (30 avril 2022) : 85–95. http://dx.doi.org/10.13170/aijst.11.1.24181.

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The hierarchical CuCo2O4-Ni(OH)2 core-shell nanowire arrays on Ni foam were fabricated using facile and cost-effective two-step hydrothermal synthesis. The growth of CuCo2O4 nanowires was developed on Ni foam as the apposite basis of the conductive scaffold, and the ultrathin Ni(OH)2 nanowires were subsequently immobilized to form CuCo2O4-Ni(OH)2 core-shell nanowire arrays (NWAs). The prepared materials were further characterized in structural, morphological, and electrochemical properties. The obtained CuCo2O4-Ni(OH)2 pseudocapacitor electrode, incorporated by unique core-shell heterostructures nanowire arrays, exhibited great specific capacitance of 1201.67 F g-1 at 1 mA g-1, which is much higher than pristine CuCo2O4 nanowire of 638.89 F g-1 at 1 mA g-1. Simultaneously, it also has a high power density of 5.56 kW kg-1 at an energy density of 73.33 Wh kg-1 and good long-term cycling performance (~84 capacitance retention after 1000 cycles). The improved morphological and structural properties have substantiated the CuCo2O4-Ni(OH)2 core-shell nanowire arrays properties owing to higher surface active area and richer redox activity for boosting the electrochemical properties.

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Li, Xiaoxin, Xiaogan Li, Ning Chen, Xinye Li, Jianwei Zhang, Jun Yu, Jing Wang et Zhenan Tang. « CuO-In2O3Core-Shell Nanowire Based Chemical Gas Sensors ». Journal of Nanomaterials 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/973156.

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The CuO-In2O3core-shell nanowire was fabricated by a two-step method. The CuO nanowire core (NWs) was firstly grown by the conventional thermal oxidation of Cu meshes at 500°C for 5 hours. Then, the CuO nanowires were immersed into the suspension of amorphous indium hydroxide deposited from the In(AC)3solution by ammonia. The CuO nanowires coated with In(OH)3were subsequently heated at 600°C to form the crystalline CuO-In2O3core-shell structure, with In2O3nanocrystals uniformly anchored on the CuO nanowires. The gas sensing properties of the formed CuO-In2O3core-shell nanowires were investigated by various reducing gases such as hydrogen, carbon monoxide, and propane at elevated temperature. The sensors using the CuO-In2O3nanowires show improved sensing performance to hydrogen and propane but a suppressed response to carbon monoxide, which could be attributed to the enhanced catalytic properties of CuO with the coated porous In2O3shell and the p-n junction formed at the core-shell interface.

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Kim, Jung Han, Seul Cham Kim, Do Hyun Kim, Kyu Hwan Oh, Woong-Ki Hong, Tae-Sung Bae et Hee-Suk Chung. « Fabrication and Characterization of ZnS/Diamond-Like Carbon Core-Shell Nanowires ». Journal of Nanomaterials 2016 (2016) : 1–6. http://dx.doi.org/10.1155/2016/4726868.

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We fabricated ZnS/diamond-like carbon (DLC) core-shell heterostructure nanowire using a simple two-step process: the vapor-liquid-solid method combined with radio frequency plasma enhanced chemical vapor deposition (rf PECVD). As a core nanowire, ZnS nanowires with face-centered cubic structure were synthesized with a sputtered Au thin film, which exhibit a length and a diameter of ~10 μm and ~30–120 nm . After rf PECVD for DLC coating, The length and width of the dense ZnS/DLC core-shell nanowires were a range of ~10 μm and 50–150 nm , respectively. In addition, ZnS/DLC core-shell nanowires were characterized with scanning transmission electron microscopy. From the results, the products have flat and uniform DLC coating layer on ZnS nanowire in spite of high residual stress induced by the high sp3fraction. To further understanding of the DLC coating layer, Raman spectroscopy was employed with ZnS/DLC core-shell nanowires, which reveals two Raman bands at 1550 cm−1(G peak) and 1330 cm−1(D peak). Finally, we investigated the optical properties from ultraviolet to infrared wavelength region using ultraviolet-visible (UV-Vis) and Fourier transform infrared (FT-IR) spectrometry. Related to optical properties, ZnS/DLC core-shell nanowires exhibit relatively lower absorbance and higher IR transmittance than that of ZnS nanowires.

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Monaico, Eduard V., Vadim Morari, Veaceslav V. Ursaki, Kornelius Nielsch et Ion M. Tiginyanu. « Core–Shell GaAs-Fe Nanowire Arrays : Fabrication Using Electrochemical Etching and Deposition and Study of Their Magnetic Properties ». Nanomaterials 12, n^o 9 (28 avril 2022) : 1506. http://dx.doi.org/10.3390/nano12091506.

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The preparation of GaAs nanowire templates with the cost-effective electrochemical etching of (001) and (111)B GaAs substrates in a 1 M HNO3 electrolyte is reported. The electrochemical etching resulted in the obtaining of GaAs nanowires with both perpendicular and parallel orientations with respect to the wafer surface. Core–shell GaAs-Fe nanowire arrays have been prepared by galvanostatic Fe deposition into these templates. The fabricated arrays have been investigated by means of scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The magnetic properties of the polycrystalline Fe nanotubes constituting the shells of the cylindrical structures, such as the saturation and remanence moment, squareness ratio, and coercivity, were analyzed in relation to previously reported data on ferromagnetic nanowires and nanotubes.

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Prete, Paola, Daniel Wolf, Fabio Marzo et Nico Lovergine. « Nanoscale spectroscopic imaging of GaAs-AlGaAs quantum well tube nanowires : correlating luminescence with nanowire size and inner multishell structure ». Nanophotonics 8, n^o 9 (10 août 2019) : 1567–77. http://dx.doi.org/10.1515/nanoph-2019-0156.

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AbstractThe luminescence and inner structure of GaAs-AlGaAs quantum well tube (QWT) nanowires were studied using low-temperature cathodoluminescence (CL) spectroscopic imaging, in combination with scanning transmission electron microscopy (STEM) tomography, allowing for the first time a robust correlation between the luminescence properties of these nanowires and their size and inner 3D structure down to the nanoscale. Besides the core luminescence and minor defects-related contributions, each nanowire showed one or more QWT peaks associated with nanowire regions of different diameters. The values of the GaAs shell thickness corresponding to each QWT peak were then determined from the nanowire diameters by employing a multishell growth model upon validation against experimental data (core diameter and GaAs and AlGaAs shell thickness) obtained from the analysis of the 3D reconstructed STEM tomogram of a GaAs-AlGaAs QWT nanowire. We found that QWT peak energies as a function of thus-estimated (3–7 nm) GaAs shell thickness are 40–120 meV below the theoretical values of exciton recombination for uniform QWTs symmetrically wrapped around a central core. However, the analysis of the 3D tomogram further evidenced azimuthal asymmetries as well as (azimuthal and axial) random fluctuations of the GaAs shell thickness, suggesting that the red-shift of QWT emissions is prominently due to carrier localization. The CL mapping of QWT emission intensities along the nanowire axis allowed to directly image the nanoscale localization of the emission, supporting the above picture. Our findings contribute to a deeper understanding of the luminescence-structure relationship in QWT nanowires and will foster their applications as efficient nanolaser sources for future monolithic integration onto silicon.

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Xiao, Ye, J. Shang, L. Z. Kou et Chun Li. « Surface deformation-dependent mechanical properties of bending nanowires : an ab initio core-shell model ». Applied Mathematics and Mechanics 43, n^o 2 (27 janvier 2022) : 219–32. http://dx.doi.org/10.1007/s10483-022-2814-6.

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AbstractAn ab initio core-shell model is proposed to evaluate the surface effect in bending nanowires, in which the elastic modulus depends on the surface relaxation and deformation induced by external loading. By using first-principles calculations based on the density functional theory (DFT), the surface and bulk properties are calculated for Ag, Pb, and Si nanowires. The obtained theoretical predictions of the effective Young’s modulus of nanowires agree well with the experimental data, which shows that the fixed-fixed nanowire is stiffened and the cantilevered nanowire is softened as the characteristic size of the cross section decreases. Furthermore, the contrastive analysis on the two kinds of nanowires demonstrates that increasing the nanowire aspect ratio would enhance the surface effect. The present results could be helpful for understanding the size effect in nanowires and designing nanobeam-based devices in nanoelectromechanical systems (NEMSs).

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Deng, Jun, Zhibiao Hao, Lai Wang, Jiadong Yu, Jian Wang, Changzheng Sun, Yanjun Han et al. « Studies on Carrier Recombination in GaN/AlN Quantum Dots in Nanowires with a Core–Shell Structure ». Nanomaterials 10, n^o 11 (20 novembre 2020) : 2299. http://dx.doi.org/10.3390/nano10112299.

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GaN quantum dots embedded in nanowires have attracted much attention due to their superior optical properties. However, due to the large surface-to-volume ratio of the nanowire, the impacts of surface states are the primary issue responsible for the degradation of internal quantum efficiency (IQE) in heterostructured dot-in-nanowires. In this paper, we investigate the carrier recombination mechanism of GaN/AlN dot-in-nanowires with an in situ grown AlN shell structure. Ultraviolet photoelectron spectroscopy (UPS) measurements were performed to describe the band bending effect on samples with different shell thicknesses. Temperature-dependent photoluminescence (TDPL) data support that increasing the AlN shell thickness is an efficient way to improve internal quantum efficiency. Detailed carrier dynamics was analyzed and combined with time-resolved photoluminescence (TRPL). The experimental data are consistent with our physical model that the AlN shell can effectively flatten the band bending near the surface and isolate the surface non-radiative recombination center. Our systematic research on GaN/AlN quantum dots in nanowires with a core–shell structure may significantly advance the development of a broad range of nanowire-based optoelectronic devices.

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Kang, Sung Bum, Rahul Sharma, Minhyeok Jo, Su In Kim, Jeongwoo Hwang, Sang Hyuk Won, Jae Cheol Shin et Kyoung Jin Choi. « Catalysis-Free Growth of III-V Core-Shell Nanowires on p-Si for Efficient Heterojunction Solar Cells with Optimized Window Layer ». Energies 15, n^o 5 (28 février 2022) : 1772. http://dx.doi.org/10.3390/en15051772.

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The growth of high-quality compound semiconductor materials on silicon substrates has long been studied to overcome the high price of compound semiconductor substrates. In this study, we successfully fabricated nanowire solar cells by utilizing high-quality hetero p-n junctions formed by growing n-type III-V nanowires on p-silicon substrates. The n-InAs0.75P0.25 nanowire array was grown by the Volmer–Weber mechanism, a three-dimensional island growth mode arising from a lattice mismatch between III-V and silicon. For the surface passivation of n-InAs0.75P0.25 core nanowires, a wide bandgap InP shell was formed. The nanowire solar cell was fabricated by benzocyclobutene (BCB) filling, exposure of nanowire tips by reactive-ion etching, electron-beam deposition of ITO window layer, and finally metal grid electrode process. In particular, the ITO window layer plays a key role in reducing light reflection as well as electrically connecting nanowires that are electrically separated from each other. The deposition angle was adjusted for conformal coating of ITO on the nanowire surface, and as a result, the lowest light reflectance and excellent electrical connectivity between the nanowires were confirmed at an oblique deposition angle of 40°. The solar cell based on the heterojunction between the n-InAs0.75P0.25/InP core-shell nanowire and p-Si exhibited a very high photoelectric conversion efficiency of 9.19% with a current density of 27.10 mA/cm2, an open-circuit voltage of 484 mV, and a fill factor of 70.1%.

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Wang, Yajun, Runhua Li, Qiaohuan Wu, Zhuang Yang, Fan Fan, Yuming Li et Guiyuan Jiang. « Enhanced Photoelectrocatalytic Activity of TiO2 Nanowire Arrays via Copolymerized G-C3N4 Hybridization ». Energies 15, n^o 12 (7 juin 2022) : 4180. http://dx.doi.org/10.3390/en15124180.

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Photoelectrocatalytic (PEC) oxidation is an advanced technology that combines photocatalytic oxidation (PC) and electrolytic oxidation (EC). PEC activity can be greatly enhanced by the PC and EC synergy effect. In this work, novel copolymerized g-C3N4 (denoted as CNx)/TiO2 core-shell nanowire arrays were prepared by chemical vapor deposition. CNx were deposited on the surface of TiO2 nanowire arrays using organic monomer 4,5-dicyanidazole and dicyandiamide as copolymerization precursor. TiO2 nanowire arrays provide a direct and fast electron transfer path, while CNx is a visible light responsive material. After CNx deposition, the light response range of TiO2 is broadened to 600 nm. The deposition of CNx shell effectively improves the PC efficiency and PEC efficiency of TiO2. Under visible light irradiation and 1 V bias potential, the rate constant k of PEC degradation of CNx/TiO2 core-shell nanowire arrays is 0.0069 min−1, which is 72% higher than that of pure TiO2 nanowires. The built-in electric field formed in the interface between TiO2 core and CNx shell would effectively promote photogenerated charge separation and PEC activity.

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Tatsuoka, Hirokazu, Wen Li, Er Chao Meng, Daisuke Ishikawa et Kaito Nakane. « Syntheses and Structural Control of Silicide, Oxide and Metallic Nano-Structured Materials ». Solid State Phenomena 213 (mars 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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Greenberg, Ya’akov, Alexander Kelrich, Shimon Cohen, Sohini Kar-Narayan, Dan Ritter et Yonatan Calahorra. « Strain-Mediated Bending of InP Nanowires through the Growth of an Asymmetric InAs Shell ». Nanomaterials 9, n^o 9 (16 septembre 2019) : 1327. http://dx.doi.org/10.3390/nano9091327.

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Controlling nanomaterial shape beyond its basic dimensionality is a concurrent challenge tackled by several growth and processing avenues. One of these is strain engineering of nanowires, implemented through the growth of asymmetrical heterostructures. Here, we report metal–organic molecular beam epitaxy of bent InP/InAs core/shell nanowires brought by precursor flow directionality in the growth chamber. We observe the increase of bending with decreased core diameter. We further analyze the composition of a single nanowire and show through supporting finite element simulations that strain accommodation following the lattice mismatch between InP and InAs dominates nanowire bending. The simulations show the interplay between material composition, shell thickness, and tapering in determining the bending. The simulation results are in good agreement with the experimental bending curvature, reproducing the radius of 4.3 µm (±10%), for the 2.3 µm long nanowire. The InP core of the bent heterostructure was found to be compressed at about 2%. This report provides evidence of shape control and strain engineering in nanostructures, specifically through the exchange of group-V materials in III–V nanowire growth.

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Ding, Yan Hong, Yuan Hong Tang et Yang Yang. « Synthesis of SiO₂ Hierarchical Nanostructure on Carbon Nanowire ». Advanced Materials Research 236-238 (mai 2011) : 1881–84. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.1881.

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A novel SiO2 hierarchical nanostructure standing on carbon nanowires is synthesized by using the hydrothermal method without any metallic catalysts. Its surface morphology, microstructure and composition are characterized by scanning electron microscopy, high-resolution transmission electron microscope and energy-dispersive spectroscope, respectively. The results show that this new nanostructure is consisted of core-shell-branches C@SiO2/SiO2. The cores are the single-crystalline carbon nanowire, and the shells and branches are the amorphous SiO2. Growth mechanisms are discussed.

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Zheng, Jinjian, Zhiming Wu, Weihuang Yang, Shuping Li et Junyong Kang. « Growth and characterization of type II ZnO/ZnSe core/shell nanowire arrays ». Journal of Materials Research 25, n^o 7 (juillet 2010) : 1272–77. http://dx.doi.org/10.1557/jmr.2010.0161.

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Type II ZnO/ZnSe core/shell nanowire arrays were grown by a two-step chemical vapor deposition. The nanowire arrays with dense nanoislands on the surface are well aligned and normal to the substrate imaged by scanning electron microscopy. The core/shell structure of nanowires was identified by a high-resolution transmission electron microscopy. The structure and composition of the shell were confirmed to be wurtzite ZnSe by x-ray diffraction, Raman scattering and energy-dispersive x-ray spectroscopy. Moreover, an intense emission was observed at 1.89 eV smaller than the band gaps of core and shell materials by photoluminescence, indicating the achievement of the type II band alignment at the interface. This study is expected to contribute to the potential applications in novel photovoltaic devices.

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Singh, Sudarshan, Subhrajit Mukherjee, Samik Mukherjee, Simone Assali, Lu Luo, Samaresh Das, Oussama Moutanabbir et Samit K. Ray. « Ge–Ge_0.92Sn_0.08 core–shell single nanowire infrared photodetector with superior characteristics for on-chip optical communication ». Applied Physics Letters 120, n^o 17 (25 avril 2022) : 171110. http://dx.doi.org/10.1063/5.0087379.

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Recent development on Ge1−xSnx nanowires with high Sn content, beyond its solid solubility limit, makes them attractive for all group-IV Si-integrated infrared photonics at the nanoscale. Herein, we report a chemical vapor deposition-grown high Sn-content Ge–Ge0.92Sn0.08 core–shell based single nanowire photodetector operating at the optical communication wavelength of 1.55 μm. The atomic concentration of Sn in nanowires has been studied using x-ray photoelectron and Raman spectroscopy data. A metal–semiconductor–metal based single nanowire photodetector, fabricated via an electron beam lithography process, exhibits significant room-temperature photoresponse even at zero bias. In addition to the high-crystalline quality and identical shell composition of the nanowire, the efficient collection of photogenerated carriers under an external electric field results in the superior responsivity and photoconductive gain as high as ∼70.8 A/W and ∼57, respectively, at an applied bias of −1.0 V. The extra-ordinary performance of the fabricated photodetector demonstrates the potential of GeSn nanowires for future Si CMOS compatible on-chip optical communication device applications.

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Yao, Hai Yan, et Guo Hong Yun. « Surface Effects on the Buckling of Nanowires Based on Modified Core-Shell Model ». Advanced Materials Research 901 (février 2014) : 3–9. http://dx.doi.org/10.4028/www.scientific.net/amr.901.3.

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In this work, surface effects including surface elasticity and residual surface stress on the buckling of nanowires are theoretically investigated. Based on modified core-shell (MC-S) model, the effective elasticity incorporating surface elasticity effect of the nanowire is derived, and by using the generalized Young-Laplace equation the residual surface stress is accounted for. The ratio of critical load with and without surface effects are obtained for a nanowire loaded in uniaxial compression. Taking silver (Ag) nanowires as an example, the analyzed results demonstrate that the influence of surface effects on the critical load of buckling becomes more and more significant as the nanowire diameter decreases. Moreover, it is shown that the influence of residual surface stress on the critical load is more prominent than that of surface elasticity.

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Meng, Xiu Qing, Feng Min Wu, Shi Hua Huang, Yun Zhang Fang et Jing Bo Li. « Influence of Shell Thickness on the Raman Properties of ZnO/ZnS Core/Shell Nanowires ». Materials Science Forum 694 (juillet 2011) : 175–79. http://dx.doi.org/10.4028/www.scientific.net/msf.694.175.

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Well aligned ZnO nanowire arrays are fabricated by a simple vapor phase transport process. Field-emission scanning electron microscopy shows the nanorods have a uniform length of about 1 um with diameters of 100 nm. After modified by ZnS, ZnO/ZnS core/shell nanowire arrays are formed and the thickness of ZnS layer increase with the increase of treatment time. X-ray diffraction analysis confirms that the as-synthesized ZnO nanorods are c-axis orientated, the modification of ZnS shell induces weak ZnS (100) diffraction peak for the treatment time of 180 min. The effects of shell thickness as a function of ZnS treatment time on the Raman scattering properties are studied. The results suggest that the coating of ZnS shell will change the Raman energy position and intensity of the ZnO nanowires, crystal lattice expansion and reconstruction of the ZnO/ZnS interface are responsible for the observed changes.

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Kumar, Arun, Seyed Ariana Mirshokraee, Alessio Lamperti, Matteo Cantoni, Massimo Longo et Claudia Wiemer. « Interface Analysis of MOCVD Grown GeTe/Sb2Te3 and Ge-Rich Ge-Sb-Te/Sb2Te3 Core-Shell Nanowires ». Nanomaterials 12, n^o 10 (10 mai 2022) : 1623. http://dx.doi.org/10.3390/nano12101623.

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Controlling material thickness and element interdiffusion at the interface is crucial for many applications of core-shell nanowires. Herein, we report the thickness-controlled and conformal growth of a Sb2Te3 shell over GeTe and Ge-rich Ge-Sb-Te core nanowires synthesized via metal-organic chemical vapor deposition (MOCVD), catalyzed by the Vapor–Liquid–Solid (VLS) mechanism. The thickness of the Sb2Te3 shell could be adjusted by controlling the growth time without altering the nanowire morphology. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to examine the surface morphology and the structure of the nanowires. The study aims to investigate the interdiffusion, intactness, as well as the oxidation state of the core-shell nanowires. Angle-resolved X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface chemistry of the nanowires. No elemental interdiffusion between the GeTe, Ge-rich Ge-Sb-Te cores, and Sb2Te3 shell of the nanowires was revealed. Chemical bonding between the core and the shell was observed.

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Vismara, Robin, Olindo Isabella, Andrea Ingenito, Fai Tong Si et Miro Zeman. « Geometrical optimisation of core–shell nanowire arrays for enhanced absorption in thin crystalline silicon heterojunction solar cells ». Beilstein Journal of Nanotechnology 10 (31 janvier 2019) : 322–31. http://dx.doi.org/10.3762/bjnano.10.31.

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Background: Elongated nanostructures, such as nanowires, have attracted significant attention for application in silicon-based solar cells. The high aspect ratio and characteristic radial junction configuration can lead to higher device performance, by increasing light absorption and, at the same time, improving the collection efficiency of photo-generated charge carriers. This work investigates the performance of ultra-thin solar cells characterised by nanowire arrays on a crystalline silicon bulk. Results: Proof-of-concept devices on a p-type mono-crystalline silicon wafer were manufactured and compared to flat references, showing improved absorption of light, while the final 11.8% (best-device) efficiency was hindered by sub-optimal passivation of the nanowire array. A modelling analysis of the optical performance of the proposed solar cell architecture was also carried out. Results showed that nanowires act as resonators, amplifying interference resonances and exciting additional wave-guided modes. The optimisation of the array geometrical dimensions highlighted a strong dependence of absorption on the nanowire cross section, a weaker effect of the nanowire height and good resilience for angles of incidence of light up to 60°. Conclusion: The presence of a nanowire array increases the optical performance of ultra-thin crystalline silicon solar cells in a wide range of illumination conditions, by exciting resonances inside the absorber layer. However, passivation of nanowires is critical to further improve the efficiency of such devices.

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Choi, Won Young, Jeong Won Kang et Ho Jung Hwang. « Cu Nanowire Structures Inside Carbon Nanotubes ». Materials Science Forum 449-452 (mars 2004) : 1229–32. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.1229.

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We have investigated the structures of copper nanowires encapsulated in carbon nanotubes using a structural optimization process applied to a steepest descent method. Results show that the stable morphology of the cylindrical ultra-thin copper nanowires in carbon nanotubes is multi-shell packs consisted of coaxial cylindrical shells. As the diameters of copper nanotubes increases, the encapsulated copper nanowires have the face centered cubic structure as the bulk. The circular rolling of a triangular network can explain the structures of ultra-thin multi-shell copper nanowires encapsulated in carbon nanotubes.

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Stankevič, Tomaš, Simas Mickevičius, Mikkel Schou Nielsen, Olga Kryliouk, Rafal Ciechonski, Giuliano Vescovi, Zhaoxia Bi et al. « Measurement of strain in InGaN/GaN nanowires and nanopyramids ». Journal of Applied Crystallography 48, n^o 2 (14 février 2015) : 344–49. http://dx.doi.org/10.1107/s1600576715000965.

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The growth and optoelectronic properties of core–shell nanostructures are influenced by the strain induced by the lattice mismatch between core and shell. In contrast with planar films, nanostructures contain multiple facets that act as independent substrates for shell growth, which enables different relaxation mechanisms. In this study, X-ray diffraction data are presented that show that InαGa1−αN shells grown on GaN cores are strained along each of the facets independently. Reciprocal space maps reveal multiple Bragg peaks, corresponding to different parts of the shell being strained along the individual facet planes. The strained lattice constants were found from the positions of the Bragg peaks. Vegard's law and Hooke's law for an anisotropic medium were applied in order to find the composition and strain in the InGaN shells. A range of nanowire samples with different InGaN shell thicknesses were measured and it is concluded that, with an In concentration of around 30%, major strain relaxation takes place when the thickness reaches 23 nm. InGaN shells of 6 and 9 nm thickness remain nearly fully strained biaxially along each of the \{10{\overline 1}0\} facets of the nanowires and the \{10{\overline 1}1\} facets of the nanopyramids.

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Vaitiekėnas, S., G. W. Winkler, B. van Heck, T. Karzig, M. T. Deng, K. Flensberg, L. I. Glazman et al. « Flux-induced topological superconductivity in full-shell nanowires ». Science 367, n^o 6485 (26 mars 2020) : eaav3392. http://dx.doi.org/10.1126/science.aav3392.

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Hybrid semiconductor-superconductor nanowires have emerged as a promising platform for realizing topological superconductivity (TSC). Here, we present a route to TSC using magnetic flux applied to a full superconducting shell surrounding a semiconducting nanowire core. Tunneling into the core reveals a hard induced gap near zero applied flux, corresponding to zero phase winding, and a gapped region with a discrete zero-energy state around one applied flux quantum, corresponding to 2π phase winding. Theoretical analysis indicates that the winding of the superconducting phase can induce a transition to a topological phase supporting Majorana zero modes. Measured Coulomb blockade peak spacing around one flux quantum shows a length dependence that is consistent with the existence of Majorana modes at the ends of the nanowire.

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Wang, Xuan Liang, En Mei Jin, Jiasheng Chen, Parthasarathi Bandyopadhyay, Bo Jin et Sang Mun Jeong. « Facile In Situ Synthesis of Co(OH)2–Ni3S2 Nanowires on Ni Foam for Use in High-Energy-Density Supercapacitors ». Nanomaterials 12, n^o 1 (23 décembre 2021) : 34. http://dx.doi.org/10.3390/nano12010034.

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Ni3S2 nanowires were synthesized in situ using a one-pot hydrothermal reaction on Ni foam (NF) for use in supercapacitors as a positive electrode, and various contents (0.3−0.6 mmol) of Co(OH)2 shells were coated onto the surfaces of the Ni3S2 nanowire cores to improve the electrochemical properties. The Ni3S2 nanowires were uniformly formed on the smooth NF surface, and the Co(OH)2 shell was formed on the Ni3S2 nanowire surface. By direct NF participation as a reactant without adding any other Ni source, Ni3S2 was formed more closely to the NF surface, and the Co(OH)2 shell suppressed the loss of active material during charging–discharging, yielding excellent electrochemical properties. The Co(OH)2–Ni3S2/Ni electrode produced using 0.5 mmol Co(OH)2 (Co0.5–Ni3S2/Ni) exhibited a high specific capacitance of 1837 F g−1 (16.07 F cm−2) at a current density of 5 mA cm−2, and maintained a capacitance of 583 F g−1 (16.07 F cm−2) at a much higher current density of 50 mA cm−2. An asymmetric supercapacitor (ASC) with Co(OH)2–Ni3S2 and active carbon displayed a high-power density of 1036 kW kg−1 at an energy density of 43 W h kg−1 with good cycling stability, indicating its suitability for use in energy storage applications. Thus, the newly developed core–shell structure, Co(OH)2–Ni3S2, was shown to be efficient at improving the electrochemical performance.

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Ursaki, Veaceslav V., Sebastian Lehmann, Victor V. Zalamai, Vadim Morari, Kornelius Nielsch, Ion M. Tiginyanu et Eduard V. Monaico. « Core–Shell Structures Prepared by Atomic Layer Deposition on GaAs Nanowires ». Crystals 12, n^o 8 (15 août 2022) : 1145. http://dx.doi.org/10.3390/cryst12081145.

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GaAs nanowire arrays have been prepared by anodization of GaAs substrates. The nanowires produced on (111)B GaAs substrates were found to be oriented predominantly perpendicular to the substrate surface. The prepared nanowire arrays have been coated with thin ZnO or TiO2 layers by means of thermal atomic layer deposition (ALD), thus coaxial core–shell hybrid structures are being fabricated. The hybrid structures have been characterized by scanning electron microscopy (SEM) for the morphology investigations, by Energy Dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis for the composition and crystal structure assessment, and by photoluminescence (PL) spectroscopy for obtaining an insight on emission polarization related to different recombination channels in the prepared core–shell structures.

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Sibirev N V, Berdnikov Y, Shtrom I. V., Ubyivovk E. V., Reznik R. R. et Cirlin G. E. « Kinetics of spontaneous formation of core shell structure in (In,Ga)As nanowires ». Technical Physics Letters 48, n^o 2 (2022) : 28. http://dx.doi.org/10.21883/tpl.2022.02.52841.18869.

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A model of spontaneous formation of the core-shell structure in (In,Ga)As nanowire grown via molecular beam epitaxy without independent radial growth is proposed. Within the framework of the proposed model, the distribution of In across the axis of the nanowire was fitted. Keywords: core-shell nanowire, ternary nanowire, InGaAs nanowire, radial nanowire heterostructure.

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Seo, Keumyoung, Taekyung Lim, Edmund M. Mills, Sangtae Kim et Sanghyun Ju. « Hydrogen generation enhanced by nano-forest structures ». RSC Advances 6, n^o 16 (2016) : 12953–58. http://dx.doi.org/10.1039/c5ra26226g.

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A hierarchical structure of one-dimensional CeO₂/SnO₂ core–shell nanowires on a three-dimensional porous disk (namely the “nanowire forest”) could maximize the reaction surface area and avoid coarsening during hydrogen generation.

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Wang, Xin, Yue Ke, Chito E. Kendrick, Xiaojun Weng, Haoting Shen, Mengwei Kuo, Theresa S. Mayer et Joan M. Redwing. « The effects of shell layer morphology and processing on the electrical and photovoltaic properties of silicon nanowire radial p+–n+junctions ». Nanoscale 7, n^o 16 (2015) : 7267–74. http://dx.doi.org/10.1039/c5nr00512d.

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Single wire p⁺–n⁺radial junction nanowire solar cell devices were fabricated by low pressure chemical vapor deposition of n⁺silicon shell layers on p⁺silicon nanowires synthesized by vapor–liquid–solid growth.

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Li, Luping, Cheng Xu, Yang Zhao et Kirk J. Ziegler. « Tin-Doped Indium Oxide-Titania Core-Shell Nanostructures for Dye-Sensitized Solar Cells ». Advances in Condensed Matter Physics 2014 (2014) : 1–6. http://dx.doi.org/10.1155/2014/903294.

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Dye-sensitized solar cells (DSSCs) hold great promise in the pursuit of reliable and cheap renewable energy. In this work, tin-doped indium oxide (ITO)-TiO2core-shell nanostructures are used as the photoanode for DSSCs. High-density, vertically aligned ITO nanowires are grown via a thermal evaporation method and TiO2is coated on nanowire surfaces via TiCl4treatment. It is found that high TiO2annealing temperatures increase the crystallinity of TiO2shell and suppress electron recombination in the core-shell nanostructures. High annealing temperatures also decrease dye loading. The highest efficiency of 3.39% is achieved at a TiO2annealing temperature of 500°C. When HfO2blocking layers are inserted between the core and shell of the nanowire, device efficiency is further increased to 5.83%, which is attributed to further suppression of electron recombination from ITO to the electrolyte. Open-circuit voltage decay (OCVD) measurements show that the electron lifetime increases by more than an order of magnitude upon HfO2insertion. ITO-TiO2core-shell nanostructures with HfO2blocking layers are promising photoanodes for DSSCs.

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Oliveira, D. S., L. H. G. Tizei, A. Li, T. L. Vasconcelos, C. A. Senna, B. S. Archanjo, D. Ugarte et M. A. Cotta. « Interaction between lamellar twinning and catalyst dynamics in spontaneous core–shell InGaP nanowires ». Nanoscale 7, n^o 29 (2015) : 12722–27. http://dx.doi.org/10.1039/c5nr02747k.

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Hiruma, K., K. Tomioka, P. Mohan, L. Yang, J. Noborisaka, B. Hua, A. Hayashida et al. « Fabrication of Axial and Radial Heterostructures for Semiconductor Nanowires by Using Selective-Area Metal-Organic Vapor-Phase Epitaxy ». Journal of Nanotechnology 2012 (2012) : 1–29. http://dx.doi.org/10.1155/2012/169284.

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The fabrication of GaAs- and InP-based III-V semiconductor nanowires with axial/radial heterostructures by using selective-area metal-organic vapor-phase epitaxy is reviewed. Nanowires, with a diameter of 50–300 nm and with a length of up to 10 μm, have been grown along the〈111〉B or〈111〉A crystallographic orientation from lithography-defined SiO2mask openings on a group III-V semiconductor substrate surface. An InGaAs quantum well (QW) in GaAs/InGaAs nanowires and a GaAs QW in GaAs/AlGaAs or GaAs/GaAsP nanowires have been fabricated for the axial heterostructures to investigate photoluminescence spectra from QWs with various thicknesses. Transmission electron microscopy combined with energy dispersive X-ray spectroscopy measurements have been used to analyze the crystal structure and the atomic composition profile for the nanowires. GaAs/AlGaAs, InP/InAs/InP, and GaAs/GaAsP core-shell structures have been found to be effective for the radial heterostructures to increase photoluminescence intensity and have enabled laser emissions from a single GaAs/GaAsP nanowire waveguide. The results have indicated that the core-shell structure is indispensable for surface passivation and practical use of nanowire optoelectronics devices.

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Han, Wei-Qiang, Dong Su, Michael Murphy, Matthew Ward, Tsun-Kong Sham, Lijun Wu, Yimei Zhu, Yongfeng Hu et Toshihiro Aoki. « Microstructure and electronic behavior of PtPd@Pt core-shell nanowires ». Journal of Materials Research 25, n^o 4 (avril 2010) : 711–17. http://dx.doi.org/10.1557/jmr.2010.0090.

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PtPd@Pt core-shell ultrathin nanowires were prepared using a one-step phase-transfer approach. The diameters of the nanowires range from 2 to 3 nm, and their lengths are up to hundreds of nanometers. Line scanning electron energy loss spectra showed that PtPd bimetallic nanowires have a core-shell structure, with a PtPd alloy core and a Pt monolayer shell. X-ray absorption near edge structure (XANES) spectra reveal that a strong Pt-Pd interaction exists in this nanowire system in that there is PtPd alloying and/or interfacial interaction. Extended x-ray absorption fine structures (EXAFS) further confirms the PtPd@Pt core-shell structure. The bimetallic nanowires were determined to be face-centered cubic structures. The long-chain organic molecules of n-dodecyl trimethylammonium bromide and octadecylamine, used as surfactants during synthesis, were clearly observed using aberration-corrected TEM operated at 80 KV. The interaction of Pt and surfactants was also revealed by EXAFS.

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Shi, Teng, Howard E. Jackson, Leigh Morris Smith, Jan M. Yarrison-Rice, Bryan Wong, Joanne Etheridge, Nian Jiang, Qiang Gao, Hark Hoe Tan et Chennupati Jagadish. « Localization of Excitons in Thin Core-Multi-Shell Quantum Well Tubes ». MRS Proceedings 1659 (2014) : 135–38. http://dx.doi.org/10.1557/opl.2014.357.

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ABSTRACTRecently, Fickenscher et al. [1] have shown that, in a core-multi-shell structure where a GaAs quantum well is embedded into an AlGaAs shell wrapped around a [111] oriented GaAs nanowire, the electron and hole ground states are strongly confined to the corners of the hexagonally symmetric quantum well. Thus this confinement defines quantum wires which run along the length of the nanowires along its corners. Here we review single nanowire photoluminescence measurements which show the significant confinement energy of the excitons. For well widths larger than 5 nm, optical transitions between electron and hole excited states can be seen in excitation spectra, while for widths less than 5 nm only the ground state optical transitions are observed. For well widths smaller than 5 nm, high resolution spatially resolved photoluminescence measurements show directly the appearance of localized states. Single nanowire spectra from the 4 nm QWT sample display ultranarrow emission lines on the high energy side of the luminescence band. Spatially-resolved PL images show that these quantum dots are localized randomly along the length of the wire.

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Garigapati, Navya Sri, et Erik Lind. « 8-band k ⋅ p modeling of strained In_xGa_(1−x)As/InP heterostructure nanowires ». Journal of Applied Physics 133, n^o 1 (7 janvier 2023) : 015701. http://dx.doi.org/10.1063/5.0133229.

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An 8-band [Formula: see text] theory is implemented for studying the electronic properties of near-surface lateral InxGa(1−x)As/InP heterostructure nanowires in the (100) direction. The change in bandgap and effective mass due to inhomogeneous strain are compared to unstrained scenario nanowires, and the lattice mismatch is varied from −3.2% to 1%. The nanowires' height is H = 5, 13 nm, and the width varies from the smallest possible width for a given height to 100 nm. The change in the bandgap exhibited a nonlinear trait with strain for all sizes of the nanowire. The tensile strain reduces the bandgap irrespective of the width of the nanowire for a given height, while the effect of compressive strain on change in the bandgap becomes width dependent. Minima and maxima in the change in effective mass with respect to the nanowire width are observed in compressively and tensile strained nanowires, respectively, due to the interplay of quantum confinement and strain. The electrical performance of a single nanowire In0.85Ga0.15As/InP MOSFET in quantum capacitance limit is discussed for various nanowire sizes. The implemented 8-band [Formula: see text] method is verified with the available experimental work and demonstrated that the developed model can be extended to study electronic parameters of arbitrarily shaped core–shell structures over a wide range of strain.

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Zhang, Wenqi, Peidong Chao, Donglei Chen, Zhan Yang et Lixin Dong. « A Core-Shell MWCNT-Pt Nanowire Electron Source with Anomalously Long-Term Stable Field Emission ». Nanomaterials 13, n^o 3 (28 janvier 2023) : 532. http://dx.doi.org/10.3390/nano13030532.

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A hybrid core-shell structured nanowire is proposed for a long-term stable electron source based on an isolated platinum/multi-walled carbon nanotube (Pt/MWCNT). This hybrid nanowire is prepared by growing a Pt shell on a metallic MWCNT through a field-emission-induced deposition (FEID) method. An in situ field emission (FE) platform was constructed inside a scanning electron microscope (SEM) equipped with two nanorobotic manipulators (NRMs) for the preparation and testing of the hybrid nanowire. An in situ fatigue test was conducted with high current intensity (500 nA) to show the influence of the Pt shell. Compared with the pristine bare MWCNT, our hybrid-nanowire-based electron source has a lifetime of hundreds of times longer and can work continuously for up to 48 h under relatively high pressure (3.6×10-3 Pa) without having an apparent change in its structure or emission currents, demonstrating good stability and tolerance to poor working conditions. The anomalous long-term stability is attributed mainly to the shielding of oxygen by Pt from the carbon shells and less heating due to the work function lowering by Pt.

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Davtyan, Arman, Thilo Krause, Dominik Kriegner, Ali Al-Hassan, Danial Bahrami, Seyed Mohammad Mostafavi Kashani, Ryan B. Lewis et al. « Threefold rotational symmetry in hexagonally shaped core–shell (In,Ga)As/GaAs nanowires revealed by coherent X-ray diffraction imaging ». Journal of Applied Crystallography 50, n^o 3 (13 avril 2017) : 673–80. http://dx.doi.org/10.1107/s1600576717004149.

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Coherent X-ray diffraction imaging at symmetrichhhBragg reflections was used to resolve the structure of GaAs/In0.15Ga0.85As/GaAs core–shell–shell nanowires grown on a silicon (111) substrate. Diffraction amplitudes in the vicinity of GaAs 111 and GaAs 333 reflections were used to reconstruct the lost phase information. It is demonstrated that the structure of the core–shell–shell nanowire can be identified by means of phase contrast. Interestingly, it is found that both scattered intensity in the (111) plane and the reconstructed scattering phase show an additional threefold symmetry superimposed with the shape function of the investigated hexagonal nanowires. In order to find the origin of this threefold symmetry, elasticity calculations were performed using the finite element method and subsequent kinematic diffraction simulations. These suggest that a non-hexagonal (In,Ga)As shell covering the hexagonal GaAs core might be responsible for the observation.

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Pan, Dong, Huading Song, Shan Zhang, Lei Liu, Lianjun Wen, Dunyuan Liao, Ran Zhuo et al. « In Situ Epitaxy of Pure Phase Ultra-Thin InAs-Al Nanowires for Quantum Devices ». Chinese Physics Letters 39, n^o 5 (1 avril 2022) : 058101. http://dx.doi.org/10.1088/0256-307x/39/5/058101.

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We demonstrate the in situ growth of ultra-thin InAs nanowires with an epitaxial Al film by molecular-beam epitaxy. Our InAs nanowire diameter (∼30 nm) is much thinner than before (∼100 nm). The ultra-thin InAs nanowires are pure phase crystals for various different growth directions. Transmission electron microscopy confirms an atomically abrupt and uniform interface between the Al shell and the InAs wire. Quantum transport study on these devices resolves a hard induced superconducting gap and 2e-periodic Coulomb blockade at zero magnetic field, a necessary step for future Majorana experiments. By reducing wire diameter, our work presents a promising route for reaching fewer sub-band regime in Majorana nanowire devices.

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Khaliava I. I, Khamets A. L., Safronov I.V., Filonov A.B. et Migas D.B. « Effect of morphology on the phonon thermal conductivity of Si, Ge, and Si/Ge core/shell nanowires ». Semiconductors 56, n^o 6 (2022) : 420. http://dx.doi.org/10.21883/sc.2022.06.53543.9780.

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An additional factor in reducing thermal conductivity for thermoelectric applications of semiconductor nanowires is a change in morphology. In this paper, for Si, Ge and core/shell Si/Ge nanowires the effect of the volume fraction and the type of core material on thermal conductivity at 300 K is investigated by means of nonequilibrium molecular dynamics. Nanowires with experimentally observed <100>, <110>, <111> and <112> orientations and different cross sections were taken into account. It was found that for <112>-oriented Si-core/Ge-shell nanowires with a core volume fraction of ~30% the thermal conductivity is the lowest (5.76 W/(m · K)), while the thermal conductivity values for pure Si and Ge nanowires are 13.8 and 8.21 W/(m · K), respectively. Keywords: nanowire, core/shell structure, morphology, silicon, germanium, thermal conductivity, molecular dynamics.

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Mohamad, Hadey K., et Hassan Traikim Badh Al Hamade. « Effects of Anisotropy and Longitudinal Field on a Ferrimagnetic Nanowire ». International Letters of Chemistry, Physics and Astronomy 53 (juillet 2015) : 64–70. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.53.64.

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A ferrimagnetic nanowire consists of the spin-1/2 core and spin-1 outer shell has been studied. The general formula for the temperature dependence of the longitudinal magnetization of the system is given. The ferrimagnetic core-shell nanowire system exhibits two and three compensation points when the temperature of the system is changed at fixed values of the anisotropy of shell sublattice and longitudinal field, respectively. The competition among the exchange coupling between the outer shell and core, the outer shell coupling, the anisotropy, the applied field, and the temperature has a considerable effect on the characteristic of magnetic properties in a two-dimensional nanowire system.

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Mohamad, Hadey, et Hassan Traikim Badh Al Hamade. « Effects of Anisotropy and Longitudinal Field on a Ferrimagnetic Nanowire ». International Letters of Chemistry, Physics and Astronomy 53 (1 juillet 2015) : 64–70. http://dx.doi.org/10.56431/p-x24w9i.

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A ferrimagnetic nanowire consists of the spin-1/2 core and spin-1 outer shell has been studied. The general formula for the temperature dependence of the longitudinal magnetization of the system is given. The ferrimagnetic core-shell nanowire system exhibits two and three compensation points when the temperature of the system is changed at fixed values of the anisotropy of shell sublattice and longitudinal field, respectively. The competition among the exchange coupling between the outer shell and core, the outer shell coupling, the anisotropy, the applied field, and the temperature has a considerable effect on the characteristic of magnetic properties in a two-dimensional nanowire system.

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Anandan, Deepak, Che-Wei Hsu et Edward Yi Chang. « Growth of III-V Antimonide Heterostructure Nanowires on Silicon Substrate for Esaki Tunnel Diode ». Materials Science Forum 1055 (4 mars 2022) : 1–6. http://dx.doi.org/10.4028/p-y19917.

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Integration of low bandgap antimonide based nanowires on Si substrate has been attracting huge attention for opto-electronic applications. In this work we demonstrated InAs/InSb and InAs/GaSb heterostructure nanowires on Si substrate by metal organic chemical vapor deposition. We grew high quality axial InSb heterostructure segment on InAs stem by self-catalyzed growth technique, which paves a way to tune the crystal structure of InSb. In case of InAs-GaSb core-shell architecture, GaSb crystal quality highly depends on InAs core. We successfully demonstrated basic electrical characteristics of InAs-GaSb core-shell nanowire which exhibits negative differential resistance at 0.8 V and peak-to-valley current ratio of 3.84.

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Kao, Yuan-Tse, Shu-Meng Yang et Kuo-Chang Lu. « Synthesis and Photocatalytic Properties of CuO-CuS Core-Shell Nanowires ». Materials 12, n^o 7 (3 avril 2019) : 1106. http://dx.doi.org/10.3390/ma12071106.

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In this study, an efficient method to synthesize CuO-CuS core-shell nanowires by two-step annealing process was reported. CuO nanowires were prepared on copper foil via thermal oxidation in a three-zone horizontal tube furnace. To obtain larger surface area for photocatalytic applications, we varied four processing parameters, finding that growth at 550 °C for 3 h with 16 °C/min of the ramping rate under air condition led to CuO nanowires of appropriate aspect ratio and number density. The second step, sulfurization process, was conducted to synthesize CuO-CuS core-shell nanowires by annealing with sulfur powder at 250 °C for 30 min under lower pressure. High-resolution transmission electron microscopy studies show that a 10 nm thick CuS shell formed and the growth mechanism of the nanowire heterostructure has been proposed. With BET, the surface area was measured to be 135.24 m2·g−1. The photocatalytic properties were evaluated by the degradation of methylene blue (MB) under visible light irradiation. As we compared CuO-CuS core-shell nanowires with CuO nanowires, the 4-hour degradation rate was enhanced from 67% to 89%. This could be attributed to more effective separation of photoinduced electron and hole pairs in the CuO-CuS heterostructure. The results demonstrated CuO-CuS core-shell nanowires as a promising photocatalyst for dye degradation in polluted water.

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Su, Yong, Xia Meng, Yiqing Chen, Qingtao Zhou, Sen Li, Xuemei Liang et Yi Feng. « Synthesis and Characterization of Al2O3/SiO2 Coaxial Nanowire Heterostructures with Periodical Twinning Structures ». Journal of Nanoscience and Nanotechnology 8, n^o 7 (1 juillet 2008) : 3483–86. http://dx.doi.org/10.1166/jnn.2008.114.

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Al2O3/SiO2 coaxial nanowire heterostructures were synthesized on a silicon substrate by a simple thermal evaporation method. The structure and morphology of the as-synthesized nanostructure were characterized using scanning electron microscopy and transmission electron microscopy. The growth of Al2O3/SiO2 coaxial nanowire heterostructures follows a vapor-solid (VS) process. Studies indicate that typical nanostructure consists of single twinning-crystalline Al2O3 nanowires (core) with diameter of about 50 nm and amorphous SiO2 shell. Photoluminescence properties were also investigated at room temperature. The photoluminescence spectrum reveals the product has a blue emission band and two UV emission bands.

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Thuong, Nguyen Thi, Nguyen Viet Minh, Nguyen Ngoc Tuan et Vu Ngoc Tuoc. « Density Functional Based Tight Binding Study on Wurzite Core-Shell Nanowires Heterostructures Zno/Zns ». Communications in Physics 21, n^o 3 (19 septembre 2011) : 225. http://dx.doi.org/10.15625/0868-3166/21/3/172.

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We present a Density Functional Based Tight Binding study on the crystallography and electronic structures of various II-VI wurtzite core-shell, core-multi-shell ZnO/ZnS unsaturated nanowires (NW) of circular and hexagonal cross sections and examine the dependence of interface stress and formation energy on nanowire lateral size with diameter range from 20$\mathring{A}$ upto 40$\mathring{A}$. Young's modulus of the wires along the axial growth direction have been estimated. Also the tensile tests have been applied for various wires to show the diameter dependences of their mechanical properties. The electronic properties of these heterostructure nanowires (e.g., Projected Band Structure, Density of State, charge transfer via Mulliken population analysis) also exhibit diameter-dependent behavior.

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Liu, Wen Fu, et Hua Li Hao. « Enhanced Absorption of Single Silicon Nanowire with Si₃N₄ Shell for Photovoltaic Applications ». Advanced Materials Research 1090 (février 2015) : 173–77. http://dx.doi.org/10.4028/www.scientific.net/amr.1090.173.

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Based on the Lorenz-Mie light scattering theory, we have calculated the light absorption of single silicon nanowire with Si3N4coating, and compared with pure single silicon nanowire. The calculated result indicates that there exists an enhanced absorption in the Si3N4-coated silicon nanowire and shows a great photocurrent enhancement factor (~70%) for the coaxial NW with the shell thickness of ~70 nm. For a special shell thickness (175 nm) in the Si3N4-coated silicon nanowire forr= 150 nm, the enhancement comes up to ~98.45%.

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van Tilburg, Marvin A. J., Wouter H. J. Peeters, Marco Vettori, Victor T. van Lange, Erik P. A. M. Bakkers et Jos E. M. Haverkort. « Polarized emission from hexagonal-silicon–germanium nanowires ». Journal of Applied Physics 133, n^o 6 (14 février 2023) : 065702. http://dx.doi.org/10.1063/5.0135215.

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We present polarized emission from single hexagonal silicon–germanium (hex-SiGe) nanowires. To understand the nature of the band-to-band emission of hex-SiGe, we have performed photoluminescence spectroscopy to investigate the polarization properties of hex-SiGe core–shell nanowires. We observe a degree of polarization of 0.2 to 0.32 perpendicular to the nanowire c-axis. Finite-difference time-domain simulations were performed to investigate the influence of the dielectric contrast of nanowire structures. We find that the dielectric contrast significantly reduces the observable degree of polarization. Taking into account this reduction, the experimental data are in good agreement with polarized dipole emission perpendicular to the c-axis, as expected for the fundamental band-to-band transition, the lowest energy direct band-to-band transition in the hex-SiGe band structure.

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