Electrical Resistivity and Thermally Stimulated Current in CuIn5Se8

From electrical resistivity measurements in the range from 240 to 450 K and from optical absorption measurements the energy gap value of CuIn₅Se₈ has been found to be 1.13 eV. Thermally stimulated current and electrical measurements at high temperature performed in indium annealed samples show deep levels at 0.55 and 0.79 eV, respectively. These defects are expected to be associated with interstitial indium or indium in copper site because of the In‐rich condition.     

Crystal Growth and Properties of the Compounds CuGa3Se5 and CuIn3Se5

CuIn₃Se₅ and CuGa₃Se₅ uniform single crystals 12 mm in diameter and 40 mm in length with the chalcopyrite‐related structure were prepared by directed crystallization of the melt. The melting points of these compounds were defined by means of the differential thermal analysis (DTA). The lattice parameters a and c as well as the axial thermal expansion coefficients α_a and α_c were determined as a function of temperature in the range from 90 to 650 K by the X‐ray diffraction method (XRD). It is found that for both the compounds the coefficients of expansion along the a ‐axis are larger than those along the c ‐axis over the entire temperature range studied.     

Electrical Properties of CuIn3Se5 Bulk Crystal at Low Temperature

CuIn₃Se₅ crystals were grown from the melt containing stoichiometric quantities of the elements of at least 5 N purity. The structure was analyzed by X‐ray powder diffraction, and shows mainly a tetragonal single phase. The chemical composition was determined by EDAX and Total X‐Ray Fluorescence (TXRF). The conductivity and the Hall effect have been measured in the temperature range from 10 to 300 K. The polar optical scattering was found to dominate at low temperatures, while in the high temperature region ionized impurity scattering mechanism was observed.     

Crystal Growth and Properties of the CuIn5S8 and AgIn5S8 Compounds

The optical and electrophysical properties as well as the structural characteristics and thermal expansion coefficients at different temperatures for the CuIn₅S₈ compound, grown by the vertical Bridgman-Stockbarger technique, and for the AgIn₅S₈ compound, prepared by the directed crystallization of the melt, were investigated.     

Ultrahigh Vacuum Atomic Layer Epitaxy of Ternary II-VI Semiconductor Compounds

A concise discussion concerning the UHV ALE growth of ternary II-VI compounds is presented in this paper. Simultaneous reflection mass spectrometry (REMS) and reflection high energy electron diffraction (RHEED) measurements of the surface kinetic and structural parameters, respectively, governing the UHV ALE growth of Cd_1-xZn_xTe and Cd_1-xMn_xTe heteroepitaxial films are reported. In addition, a Monte-Carlo-based method for simulation of the UHV ALE process of CdTe (the model-compound for this growth technique) has been used for investigation of the Cd cation's fluxes reflected from the growing epilayer surface in different phases of the ALE process. The Cd⁺ ion-related REMS signals measured during CdTe growth have been compared with the simulation results.     

Photoelectronic and electrical properties of CuIn5S8 single crystals

To identify the impurity levels in CuIn₅S₈ single crystals, the dark electrical conductivity and photoconductivity measurements were carried out in the temperature range of 50–460 K. The data reflect the intrinsic and extrinsic nature of the crystals above and below 300 K, respectively. Energy band gaps of 1.35 and 1.31 eV at 0 K and 300 K, were defined from the dark conductivity measurements and the photocurrent spectra, respectively. The dark and photoconductivity data in the extrinsic temperature region reflect the existence of two independent donor energy levels located at 130 and 16 meV. The photocurrent‐illumination intensity dependence (F) follows the law I_phαF^γ, with γ being 1.0, 0.5 and 1.0 at low, moderate and high intensities indicating the domination of monomolecular, bimolecular and strong recombination at the surface, respectively. In the intrinsic region and in the temperature region where the shallow donor energy level 16 meV is dominant, the free electron life time, τ_n, is found to be constant with increasing F. In the temperature region 140 K < T < 210 K, the free electron life time increases with increasing illumination intensity showing the supralinear character. Below 140 K, τ_n decrease with decreasing illumination intensity. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transmission electron microscopy study of hexagonal GaN film grown on GaAs (0 0 1) substrate by using AlAs nucleation layer

Hexagonal gallium nitride (h-GaN) films have been grown on AlAs nucleation layer by using radio frequency (RF) plasma source-assisted molecular beam epitaxy on GaAs (0 0 1) substrate. Transmission electron microscopy (TEM) techniques are used to characterize such h-GaN epilayers. TEM results show that (0 0 0 1) atom planes of h-GaN are parallel to (0 0 1) atom planes of the GaAs substrate. Defects, such as stacking faults and dislocations, have also been observed.     

Preparation,structure and thermal properties of CuGa5Se8

The structural parameters, the axial thermal expansion coefficients and the characteristic Debye temperatures for the order vacancy compound CuGa₅Se₈ with the chalcopyrite‐related structure, prepared by the Bridgman technique, were determined at different temperatures between 90 and 650 K by the X‐ray diffraction method. The melting point of this compound was defined from the differential thermal analysis data. The anisotropy of thermal expansion in CuGa₅Se₈ is shown to exist with the coefficients along a ‐axis being larger than those along the c ‐axis throughout the temperature range studied.     

Comparison of Transmission Electron Microscopy and X-Ray Reflectometry Data in the Study of the Structure of Silicon-Carbon Nanocomposite Films

Crystallography Reports - Vanadium-doped diamond-like silicon-carbon films have been studied by X-ray reflectometry and transmission electron microscopy. A comparison of the data obtained has shown...     

La3Ga5SiO14晶体电子结构及光学性质的第一性原理研究

采用基于密度泛函的第一性原理平面波赝势法对La3Ga5SiO14晶体基态的几何参量、能带结构、态密度和光学性质进行了系统的研究.优化了La3Ga5SiO14晶体中原子的内部坐标,利用精确计算的能带结构、态密度和电荷密度等值线分析了晶体的吸收谱、介电函数、折射率,计算结果与实验符合较好,为La3Ga5SiO14晶体材料的分子设计与应用提供了理论依据.     

The Electron Microscopic Approach to the Structure and Reactivities of Organic Solids

In this paper we continue investigations started in Refs. 1 and 2 studying the effect of a magnetic field on electrohydrodynamics of liquid crystalling complex ethers with dielectric constant anisotropy close to zero. The investigations were made with 100 μm thick layers having initial planar “first” structure of B and C mixtures described in Ref. 2.

Figure 1 shows dependences of optical layer transmittance on the intensity of the magnetic field (H) directed normal to bearing surfaces, and in the absence of an electric field in the absence of an electric field (curves I and II). For some threshold values H = H_th all the samples showed an increased transmission arising due to Fredericks transition.³     

Electron microscopy investigations on structures of ZrO2‐rich phases in the quasibinary system ZrO2‐Zr3N4

Slowly cooled nitrided zirconia samples were investigated and characterized by means of transmission electron microscopy (TEM). Besides the well‐known different modifications of ZrO₂ some ZrO₂‐rich oxynitride phases could be further found, called β‐type phases. An overview regarding the formation of such different structural modifications could be gained, supported by previously performed measurements using powder X‐ray diffractometry (XRD). Similar to fast cooled nitrided zirconia samples Zr(N,O), the slowly cooled ones also contain different kinds of ZrO₂ precipitates, which can be obviously emphasized by using the methods of diffraction contrast. A super cell was successively built, derived from the unit cells of the β and β′ phase, in order to explain the structure of the observed modulated β″ phase. Agreements from the comparisons between experimental high resolution images and the simulated ones of such modulated structures confirm the suggested starting points. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

ZrO2/Fe3Al复合材料的界面电子结构计算及材料制备

采用热压烧结制备了ZrO2(3Y)/Fe3Al复合材料,材料的室温抗弯强度、断裂韧性、HRA硬度分别为1321MPa、39MPa*m1/2、86.7,临界热震温差(ΔT)由单相ZrO2(3Y)的250℃提高至500℃.在此基础上,用EET理论(经验电子理论)计算了ZrO2与Fe3Al的价电子结构及其部分晶面的电子密度,并对两相的晶体学取向进行了预测.     

LiZr2(PO4)3包覆对高镍三元正极材料结构及电化学性能的影响

高镍三元正极材料LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)具有优异的放电能力。但其存在锂镍混排严重、结构稳定性差导致的容量衰减快等问题。为解决这些问题,本论文首先合成NCM811三元正极材料,再利用湿法涂覆的方法将磷酸锆锂LiZr₂(PO₄)₃(LZPO)包覆在NCM811三元正极材料的表面,形成LZPO@NCM811三元正极改性材料,并对改性前后的NCM811三元正极材料结构和电化学性能进行研究。研究结果表明,在NCM811表面包覆1%LZPO得到样品的结构最稳定,材料的电化学性能最好:在0.1 C倍率下,首圈放电容量为210.16 mAh/g,远高于未改性NCM811材料(201.01 mAh/g);在循环200圈后,材料的容量保持率为79.4%,优于未改性的NCM811材料(容量保持率为60.0%)。     

非线性光学晶体BaBPO5的生长、结构研究

本文采用顶部籽晶高温溶液法,以Li4P2O7为助熔剂,生长了大尺寸BaBPO5单晶.进行了BaBPO5晶体的结构测定,结果表明该晶体属三方晶系,空间群:P3221,晶胞参数为a=b=0.71329(10)nm,c=0.70368(14)nm,α=β=90°,γ=120°, Z=3.该晶体结构中沿[001]方向存在BO4四面体链,每一个硼氧四面体用它的两个顶点分别与两个PO4四面体相连组成螺旋状的链.硼氧四面体、磷氧四面体和钡氧多面体结合在一起形成一个三维网络结构.同时,对BaBPO5的粉末倍频效应进行了研究.     

热注入法合成PbX(X=S,Se)量子点的结构和性能研究

采用热注入的方法在空气氛围中合成PbX(X=S,Se)量子点,液体石蜡和磷酸三丁酯(TBP)作为不同的溶剂优化PbSe量子点的合成;使用六甲基二硅硫烷(TMS)作为硫源合成了第一激子吸收峰在900 ～ 1500 nm分布的PbS量子点.通过透射电镜(TEM)、X射线衍射(XRD)和吸收光谱等测试手段对合成的物质进行成分与光学性能分析表征,对比研究了Ⅳ-Ⅵ族化合物量子点在成核过程中的差异.结果表明在相同的实验条件下PbS量子点的反应条件相对温和,量子限域效应明显;而PbSe量子点的合成对环境的要求更加严苛,反应温度更高,量子点的尺寸分布更宽.     

Structure of the product formed via Cu(I)-promoted oxidative dimerization ofexo-8-ethynylpentacyclo[5.4.0.02,6.03,10.05.9]undecan-endo-8-ol

The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units.     

Co包覆纳米Al2 O3/TiC复合材料的界面电子结构计算及材料制备

采用热压烧结法制备了Co包覆纳米Al2O3/TiC复合材料.当热压烧结温度为1650℃时,复合材料的抗弯强度、断裂韧性和硬度分别为782MPa、7.81MPa*m1/2和HRA92.7.Al2O3和Al2O3/TiC的断口以沿晶断裂为主,Co包覆Al2O3/TiC复合材料的断口则为沿晶和穿晶混合断口.利用经验电子理论计算了Co、TiC与α-Al2O3三者的价电子结构及其部分晶面的电子密度,并对三相的晶体学取向进行了预测.     

手性大孔磷酸镓Hit-5的水热合成与晶体结构

本文采用水热合成法制备了一个三维手性大孔开放骨架磷酸镓Ga16P16O75·4[1,6-C6H18N2]·[C2H10N2]·2H2O(简称Hit-5).反应起始原料摩尔配比为:1 GaOOH:15 H3PO4:7.5 H2N(CH2)6NH2:0.5 C2H8N2:555 H2O.Hit-5属正交晶系,P21212空间群,晶胞参数:a=0.8671(1)nm,b=1.7945(1)nm,c=0.9101(1)nm,β=108.33(1)°,V=1.3443(2)nm3,Z=4.Hit-5的骨架是由Ga3P3六聚体和Ga4P4八聚体两个不同的二级结构单元通过共顶点联接构成三维纳米孔结构,在[001]方向呈现16-元环孔道.     

CNGS和CTGS晶体电子结构及成键特性的第一性原理研究

采用基于密度泛函的第一性原理平面波赝势法对CNGS和CTGS基态的几何结构、电子结构和成键特性进行了系统的研究;利用精确计算的能带结构、态密度和所绘制的电荷密度等值线分析了晶体中各元素对总态密度的贡献和杂化特性和晶体中各阳离子的成键强度和特点;排列出各键的强弱顺序并指出C位(Ga-O键)、B位(X-O键)和D位(Si-O键)是晶体压电特性的主要来源;计算了其折射率,并与实验数据进行了比较,计算误差小于9;.