Tunable structure,morphology of Zn1−xMgxO fine powder prepared by spray pyrolysis method and its luminescence properties

In this report, the role of Magnesium on the crystal structure, morphology, and its luminescence properties of Zn_1−xMg_xO particle were investigated. The Zn_1−xMg_xO particle was prepared by spray pyrolysis method. The obtained particle was analyzed using XRD, SEM-EDS, and photoluminescence spectroscopy correspondingly for crystal structure, morphology and elemental analysis, and photoluminescence properties due to the presence of magnesium dopant. The XRD results showed that the original structure of the particle is hexagonal wurtzite and change to cubical as the increase of Mg. The a- lattice parameter increased, and c- lattice parameter decreased with increasing the concentration of Mg in wurtzite crystal. The SEM results exhibited different morphology of the resulting particle. The morphology of the sample is dense with wrinkled shape and is changing to spherical as the result of Mg incorporation into the crystal. Photoluminescence study revealed that the addition of Mg affects the existence of new energy state beside native defect of ZnO in between valence and conduction band. The widening of bandgap on Zn_1−xMg_xO is due to the blue shift of excitonic peak in the excitation spectrum that usually called Burstein-Moss effect.     

Structural,optical, thermoelectrical,and magnetic study of Zn1‐xCoxO (0 ≤ x ≤ 0.10) nanocrystals

In this work, we have prepared Co‐doped ZnO nanocomposites by zinc nitrate and cobalt sulfate as new precursors via the coprecipitation method and the samples were followed to identify the morphological, optical, structural, and magnetic properties. The XRD patterns revealed the crystalline nature of nanoparticles with hexagonal wurtzite structures, which meant that Co impurity did not disturb the structure of pure ZnO and the minimum crystallite size of nanoparticles was calculated to be around 37 nm. The XRD patterns also showed the lattice parameter increase owing to the incorporation of a Co dopant. The TEM results revealed the sphere‐like particles whose size varied between 56 and 88 nm in diameter at a 4% level of impurity. DRS analysis identified that the band gap energy decreased from 3.18 eV for the pure substance to 2.36 eV for the 10% impure substance. VSM analysis exhibited that the saturation magnetization value increased to 8.4 × 10^?3 emu/g for the highest Co content of 10%, which indicated the ferromagnetic behavior of NPs.     

Realization of Wurtzite GaSb Using InAs Nanowire Templates

The crystal structure of a material has a large impact on the electronic and material properties such as band alignment, bandgap energy, and surface energies. Au‐seeded III–V nanowires are promising structures for exploring these effects, since for most III–V materials they readily grow in either wurtzite or zinc blende crystal structure. In III–Sb nanowires however, wurtzite crystal structure growth has proven difficult. Therefore, other methods must be developed to achieve wurtzite antimonides. For GaSb, theoretical predictions of the band structure diverge significantly, but the absence of wurtzite GaSb material has prevented any experimental verification of the properties. Having access to this material is a critical step toward clearing the uncertainty in the electronic properties, improving the theoretical band structure models and potentially opening doors toward application of this material. This work demonstrates the use of InAs wurtzite nanowires as templates for realizing GaSb wurtzite shell layers with varying thicknesses. The properties of the axial and radial heterointerfaces are studied at the atomic scale by means of aberration‐corrected scanning transmission electron microscopy, revealing their sharpness and structural quality. The transport characterizations point toward a positive offset in the valence bandedge of wurtzite compared to zinc blende.     

Unravelling a solution-based formation of single-crystalline kinked wurtzite nanowires: The case of MnSe

The search for a novel strategy to sculpt semiconductor nanowires (NWs) at the atomistic scale is crucial for the development of new paradigms in optics,electronics,and spintronics.Thus far,the fabrication of single-crystalline kinked semiconductor NWs has been achieved mainly through the vapor-liquid-solid growth technique.In this study,we developed a new strategy for sculpting single-crystalline kinked wurtzite (WZ) MnSe NWs by triggering the nonpolar axial-oriented growth,thereby switching—at the atomistic scale—the NW growth orientation along the nonpolar axes in a facile solution-based procedure.This presents substantial challenges owing to the dominant polar c axis growth in the solution-based synthesis of one-dimensional WZ nanocrystals.More significantly,the ability to continuously switch the nonpolar axial-growth orientation allowed us to craft the kinking landscape of types 150°,120°,90°,and 60°.A probabilistic analysis of kinked MnSe NWs reveals the correlations of the synergy and interplay between these two sets of nonpolar axial growth-orientation switching,which determine the actual kinked motifs.Furthermore,discriminating the side-facet structures of the kinked NWs significantly strengthened the spatially selected interaction of Au nanoparticles.We envisage that such a facile solution-based strategy can be useful for synthesizing other single-crystalline kinked WZ-type transition-metal dichalcogenide NWs to develop novel functional materials with finely tuned properties.     

Solid-State Phase Equilibria in the ZnS-Ga2S3 System

The ZnS-Ga₂S₃ equilibrium phase diagram has been determined to 50 mol% over the temperature range 700° to 900°C. Samples of various compositions were prepared via solid-state diffusion starting from powders of the pure components. The identification of the phases was determined by X-ray diffraction methods. The principal feature of the phase equilibria is the eutectoid transformation at 818 ± 5°C of hexagonal wurtzite containing 16 ± 1 mol% Ga₂S₃ to cubic ZnS and tetragonal ZnGa₂S₄. ZnGa₂S₄ is the equilibrium compound at 50 mol% Ga_zS₃, but it exists over a considerable range of stoichiometry. The solubility of Ga₂S₃ in ZnS increases with increasing temperature to a maximum of 9 ± 1 mol% at the eutectoid temperature.     

电场下应变纤锌矿GaN/AlxGa1-xN异质结中束缚极化子的压力效应

对应变纤锌矿GaN/AlxGa1-xN异质结系统,引入简化相干势近似,利用改进的LLP变换和变分法计算了流体静压力和外场作用下束缚极化子的结合能。考虑由于晶格失配所致的单、双轴应变以及界面光学声子模和半空间光学声子模与电子和杂质之间的相互作用,讨论了结合能随压力、杂质位置和流体静压力的变化关系以及声子对于斯塔克能量移动的影响。数值计算结果表明,高频支界面声子模和类LO半空间声子模对于结合能和斯塔克能移的影响是主要的,且随压力的增加而显著增大,而低频支界面声子模和类TO声子模的作用则很小,且对于杂质位置和流体静压力的变化不敏感。计算还表明,导带的弯曲也不容忽视。     

Pressure influence on bound polarons in a strained wurtzite GaN/AlxGa1-xN heterojunction under an electric field

The binding energies of bound polarons near the interface of a strained wurtzite GaN/AlxGa1-xN heterojunction are studied by using a modified LLP variational method and a simplified coherent potential approximation under hydrostatic pressure and an external electric field.Considering the biaxial strain due to lattice mismatch or epitaxial growth,the uniaxial strain effects and the influences of the electron-phonon interaction as well as impurity-phonon interaction including the effects of interface-optical phonon modes and half-space phonon modes,the binding energies as functions of pressure,the impurity position,areal electron density and the phonon effect on the Stark energy shift are investigated.The numerical result shows that the contributions from the interface optical phonon mode with higher frequency and the LO-like half space mode to the binding energy and the Stark energy shift are important and obviously increase with increasing hydrostatic pressure,whereas the interface optical phonon mode with lower frequency and the TO-like half space mode are extremely small and are insensitive to the impurity position and hydrostatic pressure.It is also shown that the conductive band bending should not be neglected.     

Polar Quasi-Confined Optical Phonon Modes in Wurtzite Quasi-One-Dimensional GaN/AlxGa1-xN Quantum Well Wires

基于介电连续模型与Loudon的单轴晶体模型,推导分析了纤锌矿准一维量子阱线中的准受限(QC)光学声子模及相应的电子-QC光学声子之间的相互作用函数.对一个AlN/GaN/AlN纤锌矿量子阱线进行了数值计算.结果显示,当体系的角量子数m与z方向上的自由波数kz较小时,QC光学声子模的色散相当明显.观察到纤锌矿量子体系中的QC光学声子模的“退化”行为.通过电子-QC光学声子之间的耦合函数的讨论发现,高频区中的低频支QC模在电子-QC光学声子模之间的相互作用中起主要作用.计算结果还证明自由波数kz与角量子数m对电子-QC光学声子模间的耦合特性具有相似的影响.