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Simulation of GaAs Nanowire Growth and Crystal Structure
摘要： Growing GaAs nanowires with well defined crystal structures is a challenging task, but may be required for the fabrication of future devices. In terms of crystal phase selection, the connection between theory and experiment is limited, leaving experimentalists with a trial and error approach to achieve the desired crystal structures. In this work, we present a modelling approach designed to provide the missing connection, combining classical nucleation theory, stochastic simulation and mass transport through the seed particle. The main input parameters for the model are the flows of the growth species and the temperature of the process, giving the simulations the same flexibility as experimental growth. The output of the model can also be directly compared to experimental observables, such as crystal structure of each bilayer throughout the length of the nanowire and the composition of the seed particle. The model thus enables for observed experimental trends to be directly explored theoretically. Here, we use the model to simulate nanowire growth with varying As flows, and our results match experimental trends with good agreement. By analysing the data from our simulation, we find theoretical explanations for these experimental results, providing new insights into how the crystal structure is affected by the experimental parameters available for growth.
关键词： Wurtzite,Zinc Blende,GaAs,Nanowire,Simulation
更新于2025-09-23 15:23:52
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Fabricating ZnSnN2 with cosputtering
摘要： The deposition of ZnSnN2 by co-sputtering was studied systematically. Different deposition parameters, including substrate temperatures, N2 flow rates and different work pressure etc. were tried and the structural, optical and electrical properties were studied. The results show that the deposition parameters to fabricate ZnSnN2 are relatively wide. The suitable substrate temperature to obtain polycrystalline ZnSnN2 is around 350 °C when other parameters are kept constant. Relatively larger N2 flow rate can suppress the formation of metallic phase such as Sn and favour the deposition of ZnSnN2 with relatively pure phase, with other parameters to be constant. The addition of the substrate bias voltage or a relatively lower power of the Sn target is harmful to the film crystallization of ZnSnN2. The samples are considered to be wurtzite due to the absence of the orthorhombic (110) and (011) peaks at 20°–22°. The hexagonal lattice constants a and c are about 3.36–3.40 ? and 5.49 ?, respectively. The sputtering pressure can affect the structural and electrical properties of ZnSnN2. ZnSnN2 prepared at larger work pressure such as 7.0 Pa has a lower electron density (6.72 × 10^19 cm^-3) and a higher mobility (24.3 cm^2 V^-1 s^-1) as compared with those prepared at 1.0 and 3.0 Pa.
关键词： Sputtering,Wurtzite,Degenerate,ZnSnN2,Mobility
更新于2025-09-23 15:23:52
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General condition for realizing a collinear spin-orbit effective magnetic field in two-dimensional electron systems and its application to zinc-blende and wurtzite quantum wells
摘要： In this paper, we have studied two-dimensional (2D) electron systems described by the effective Hamiltonians containing spin-orbit coupling (SOC) terms up to an arbitrary odd order in wave vector k. The general condition for realizing a SOC-induced effective magnetic field (SOF) in such systems, formulated only in terms of the SOC parameters, is derived. When this condition is satisfied, the projection of the electron spin on the direction of the collinear SOF is a conserved quantity. The complete set of the k-linear and k-cubic Dresselhaus SOC contributions to the effective 2D Hamiltonian of an arbitrarily oriented zinc-blende quantum well is computed by a proper averaging of the corresponding tight-binding bulk SOC Hamiltonian. We investigate possibilities for realization of the collinear SOF in zinc-blende quantum wells of different orientation and obtain some interesting findings, which supplement the results of earlier works. Application of the developed formalism to wurtzite semiconductor 2D systems shows that the collinear SOF can be also realized in a wide class of such quantum wells.
关键词： effective magnetic field,spin-orbit coupling,quantum wells,wurtzite,zinc-blende
更新于2025-09-23 15:23:52
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Phase-Selective Synthesis of CIGS Nanoparticles with Metastable Phases Through Tuning Solvent Composition
摘要： I-III-VI2 compounds have shown great interests in the application of functional semiconductors. Among them, Cu(In,Ga)S2 has been a promising candidate due to its excellent optoelectronic properties. Although the polymorphs of Cu(In,Ga)S2 have been attracted extensive attentions, the efforts to developing the methodologies for phase-controlled synthesis of them are rare. In this paper, we reported a phase-selective synthesis of CIGS nanoparticles with metastable phases via simply changing the composition of solvents. For the wet chemistry synthesis, the microstructure of the initial nuclei is decisive to the crystal structure of final products. In the formation of Cu(In,Ga)S2, the solvent environment is the key factor, which could affect the coordination of monomers and influence the thermodynamic conditions of Cu-S nucleation. Moreover, wurtzite and zincblende Cu(In,Ga)S2 nanoparticles are selectively prepared by choosing pure en or its mixture with deionized water as reaction solvent. The as-synthesized wurtzite Cu(In,Ga)S2 possess a band gap of 1.6 eV and a carrier mobility of 4.85 cm2/Vs, which indicates its potential to construct a heterojunction with hexagonal-structured CdS for solar cells.
关键词： Nanoparticles,Wurtzite,Phase-selective,Zincblende,Metastable,CIGS
更新于2025-09-23 15:21:01
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Atomistic theory of electronic and optical properties of InAsP/InP nanowire quantum dots
摘要： We present here an atomistic theory of the electronic and optical properties of hexagonal InAsP quantum dots in InP nanowires in the wurtzite phase. These self-assembled quantum dots are unique in that their heights, shapes, and diameters are well known. Using a combined valence-force-field, tight-binding, and configuration-interaction approach we perform atomistic calculations of single-particle states and excitonic, biexcitonic, and trion complexes as well as emission spectra as a function of the quantum dot height, diameter, and As versus P concentration. The atomistic tight-binding parameters for InAs and InP in the wurtzite crystal phase were obtained by ab initio methods corrected by empirical band gaps. The low energy electron and hole states form electronic shells similar to parabolic or cylindrical quantum confinement, only weakly affected by hexagonal symmetry and As fluctuations. The relative alignment of the emission lines from excitons, trions, and biexcitons agrees with that for InAs/InP dots in the zincblende phase in that biexcitons and positive trions are only weakly bound. The random distribution of As atoms leads to dot-to-dot fluctuations of a few meV for the single-particle states and the spectral lines. Due to the high symmetry of hexagonal InAsP nanowire quantum dots the exciton fine structure splitting is found to be small, of the order a few μeV with significant random fluctuations in accordance with experiments.
关键词： fine structure splitting,electronic properties,optical properties,emission spectra,tight-binding,single-particle states,excitonic complexes,InAsP quantum dots,InP nanowires,wurtzite phase,configuration-interaction,valence-force-field,atomistic theory
更新于2025-09-23 15:19:57
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The effect of indium doping on photovoltaic properties of chemically synthesized zinc oxide thin-film electrodes
摘要： Photovoltaic (PV) performance of chemically synthesized indium-doped zinc oxide (IZO) nanorod electrodes has been investigated by photocurrent density-voltage (J-V). The indium (In) concentration was varied from 2 to 6 at.% for IZO. The J-V measurements as performed under a dark condition and a simulated white light of 80 mW/cm2 confirmed increase in PV performance with the IZO electrodes, making a peak with the 4 at.% In concentration. The investigated properties of the synthesized In-doped ZnO nanorod electrodes (structural and optical) strongly agreed with the PV results and well support the enhanced PV performance of the IZO electrodes. This clearly indicates that IZO electrodes would be preferred against undoped ones in PV solar cell application.
关键词： IZO electrodes,Photovoltaic performance,In concentration,Wurtzite crystal structure,ZnO nanorods
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Wurtzite InGaN/GaN Quantum Dots for Intermediate Band Solar Cells
摘要： Wurtzite InGaN quantum dots in GaN are investigated for intermediate band solar cells. A global limiting power conversion ef?ciency of 44% is predicted through detailed balance calculations with full freedom of allowed subgap transitions. We consider cylindrical quantum dots, predicting band structures using an 8-band k.p model, including deformation potential and piezoelectric ?elds from induced lattice strain. Taking the energy levels from the k.p model as absorption cutoffs in the detailed balance calculation, we determine the best device ef?ciency possible as a function of indium fraction and dot size. For small dots, of size ≈ 50 ?A and indium fraction ≈ 0.7, ef?ciencies up to 42% are in principle attainable under 1-sun illumination.
关键词： Quantum Dots,Intermediate Band Solar Cells,Detailed Balance Calculations,8-band k.p model,Wurtzite InGaN
更新于2025-09-11 14:15:04
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Concurrent Zinc-Blende and Wurtzite Film Formation by Selection of Confined Growth Planes
摘要： Recent research on nanowires (NWs) demonstrated the ability of III-V semiconductors to adopt a different crystallographic phase when they are grown as nanostructures, giving rise to a novel class of materials with unique properties. Controlling the crystal structure however remains difficult and the geometrical constraints of NWs cause integration challenges for advanced devices. Here, we report for the first time on the phase-controlled growth of micron-sized planar InP films by selecting confined growth planes during template-assisted selective epitaxy. We demonstrate this by varying the orientation of predefined templates, which results in concurrent formation of zinc-blende (ZB) and wurtzite (WZ) material exhibiting phase purities of 100% and 97%, respectively. Optical characterization revealed a 70 meV higher band gap and a 2.5x lower lifetime for WZ InP in comparison to its natural ZB phase. Further, a model for the transition of the crystal structure is presented based on the observed growth facets and the bonding configuration of InP surfaces.
关键词： template-assisted selective epitaxy,zinc-blende,crystal structure,indium phosphide,wurtzite
更新于2025-09-10 09:29:36
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Synthesis of Curved CuIn1-xGax(S1-ySey)2 Nanocrystals and Complete Characterization of their Diffraction Contrast Effects
摘要： Herein, we report the synthesis and complete structural characterization of curved CuIn1-xGax(S1-ySey)2 (x = y = 0.5) nanocrystals, which adopt a 2D nanoplate morphology and crystallize in the hexagonal wurtzite phase. A detailed transmission electron microscopy (TEM) analysis reveals that the 2D nanoplates are predominately [001]-oriented and exhibit a unique bend contour pattern, due to curvature on the (001) basal plane. The contrast behavior of bend contours in this system is further supported through specimen tilting experiments inside the TEM, in combination with dark-field (DF) imaging in both TEM and scanning TEM (STEM) modes. This bending is believed to originate from the proximity effect of the top and bottom (001) surfaces.
关键词： bend contours,CuIn1-xGax(S1-ySey)2,hexagonal wurtzite phase,TEM,nanocrystals
更新于2025-09-09 09:28:46
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Propose for Raman mode position for Mn-doped ZnO nanoparticles
摘要： Raman scattering used to study Mn-doped ZnO and pressurized Mn-doped ZnO for various dopant concentrations and pressures. Since none of the Zn sites are preferred to other Zn sites by default, the likelihood of replacing Zn with Mn is the same for each Zn site in the ZnO lattice. That is, Mn substitution should be visible throughout the Raman spectrum of ZnO with different degrees of effectiveness due to Mn substitution. We observe this affection in two different regions related to Zn -and O- regions. We believe if we want to see the effect of Mn doping these two regions must be considered. Based on this belief, we disagree with some of the previous Mn-related modes assignment. These modes are either due to combinations modes of ZnO itself or to silent modes of ZnO activated under Raman selection rules caused by the breakdown of the translational symmetry of the crystal lattice.
关键词： Raman scattering,Mn dopant,Wurtzite structure,Pressure
更新于2025-09-04 15:30:14