结合高分辨率X射线光电子能谱和拉曼散射研究GexGa8S92-x玻璃结构

本文在固定Ga原子含量为8%的情况下,结合高分辨率X射线光电子能谱和拉曼散射光谱对硫系玻璃Ge_xGa₈S_92-x(x=24%,26.67%,29.6%,32%和36%)的结构进行了研究.通过分析玻璃结构中各单元结构的演变情况,发现玻璃内部网络结构主要为S原子桥接GeS₄和GaS₄四面体结构.随着Ge含量的逐渐增大,S链状或环状结构单元迅速减少,并消失于Ge_26.67Ga₈S_65.33玻璃组分中;而类乙烷结构S₃Ge-GeS₃中的Ge—Ge同极键和S3Ge/Ga-Ga/GeS3结构中的M—M (Ge—Ge,Ga—Ga或Ge—Ga)同极键同时出现于Ge_29.6Ga₈S_62.4玻璃中,并且其结构数量随着Ge含量的增大而逐渐增加.由此可以判定,首先,在硫系玻璃Ge_xGa₈     

元素取代对Ge-As(Sb)-Se玻璃转变阈值行为的影响

本文针对Sb取代As元素对Ge_xAs(Sb)₂₀Se_80–x玻璃阈值行为的影响进行研究.对理想共价网络玻璃Ge_xAs₂₀Se_80–x的玻璃转变温度、密度和折射率等物理参数进行了系统测量,在其平均配位数为2.4和2.67处验证了转变阈值的存在,这两个转变分别代表玻璃内部的共价网络结构从欠限制的松散状态到过限制的紧致状态的转变和从二维到三维紧致状态的转变.但是,当金属性更强的Sb取代As时,得到的非理想共价网络玻璃Ge_xSb₂₀Se_80–x则会引起转变阈值的变化,转变阈值改变为化学计量组成.进一步利用拉曼散射技术对其结构进行表征,并将拉曼光谱通过分峰拟合分解成不同的结构单元的特征峰,它们各自的强度变化表现出相同的行为,这归因于As和Sb的原子半径差异较大所引起的化学效应以及Sb元素具有较强的离子特性.     

In0.3Co4Sb12-xSex 方钴矿热电材料的制备和热电性能

用熔融退火结合放电等离子烧结法制备了In_0.3Co₄Sb_12-xSe_x(x=0—0.3)方钴矿热电材料,探讨了In的存在形式,系统研究了Se掺杂量对结构和热电性能的影响.结果表明:In可以填充到方钴矿二十面体空洞处,过量In在晶界处形成InSb第二相,Se对Sb的置换使晶格常数减小,In填充上限降低;In_0.3Co₄Sb_12-xSe_x样品呈n型传导,随着Se掺杂量的增大,载流子浓度降低,电导率下降,Seebeck系数增大,功率因子有所降低;由于在结构中引入了质量波动及晶格畸变,适量的Se掺杂可以大幅降低材料晶格热导率;样品In_0.3Co₄Sb₁₂和In_0.3Co₄Sb_11.95Se_0.05的最大ZT值均达到1.0以上. 关键词： 掺杂 填充式方钴矿 热电性能     

GeSe2-Sb2Se3-CsCl玻璃的光学性质与析晶动力学研究

采用熔融淬冷法制备了20GeSe₂-（80-x）Sb₂Se₃-xCsCl（x=2,4,8,10 mol%）硫卤玻璃系统,测试了样品在可见至中远红外区域的透过光谱,研究了硫卤玻璃中CsCl对玻璃短波吸收限的影响;并测试了典型的20GeSe₂-76Sb₂Se₃-4CsCl样品在不同升温速率下的DTA曲线,利用非等温方法研究了其析晶动力学; 关键词： 硫卤玻璃 非等温过程 析晶动力学     

钙钛矿结构La0.9Sb0.1MnO3的庞磁电阻性质

一种新的钙钛矿结构的庞磁电阻氧化物La_0.9Sb_0.1MnO₃已用固态反应方法制 成，通过超导量子干涉器件(SQUID)装置测量研究了它的电输运性质和磁性质.x射线光电子 能谱分析证明，该氧化物中Sb的价态是+5价，因此该氧化物是一种新的电子掺杂型庞磁电阻 材料. 关键词： 钙钛矿结构 0.9Sb_0.1MnO₃')" href="#">La_0.9Sb_0.1MnO₃ 电子掺杂 庞磁电阻     

S取代Se对Ge_(11.5)As_(24)Se_(64.5–x)S_x玻璃结构及光学性质的影响

本文制备了硫系玻璃Ge_(11.5)As_(24)Se_(64.5–x)S_x (x=0, 16.125%, 32.25%, 48.375%和64.5%)并研究了其光学性质,目的在于筛选可用于光学器件的最佳组分.通过测试该系列玻璃的激光损伤阈值、折射率、三阶非线性折射率以及吸收光谱,结果发现,玻璃中的Se被S原子逐渐替代后,玻璃的线性和三阶非线性折射率逐渐降低,玻璃光学带隙和激光损伤阈值不断升高.我们进一步利用拉曼散射光谱和高分辨率X射线光电子能谱研究导致这些物理性能变化的结构起源,通过分析玻璃中不同结构单元的演变过程,发现在这些玻璃网络结构中均以异极键(Ge—Se/S, As—Se/S)为主,且相对于Se而言, Ge和As优先与S结合成键.随着玻璃结构中S/Se比例的增加,与Se相关的化学键(Ge—Se,As—Se和Se—Se)数量逐渐减少, S相关化学键(Ge—S,As—S和S—S)数量逐渐增加,但这对玻璃的拓扑结构几乎没有影响.由此可以断定引起玻璃物理性质变化的主要原因是玻璃结构体系中各个化学键强度之间的差异.     

Ge20Sb15Se65薄膜的热致光学特性变化研究

采用磁控溅射法制备了Ge₂₀Sb₁₅Se₆₅薄膜, 研究热处理温度(150—400 ℃)对薄膜光学特性的影响. 通过分光光度计、X射线衍射仪、显微拉曼光谱仪对热处理前后薄膜样品 的光学特性和微观结构进行了表征, 并根据Swanepoel方法以及Tauc公式分别计算了薄膜折射率色散曲线和光学带隙等参数. 结果表明当退火温度(T_a)小于薄膜的玻璃转化温度(T_g)时,薄膜的光学带隙(E_g^opt)随着退火温度的增加由1.845 eV上升至1.932 eV, 而折射率由2.61降至2.54; 当退火温度大于薄膜的玻璃转化温度时,薄膜的光学带隙随退火温度的增加由1.932 eV降至1.822 eV, 折射率则由2.54增至2.71. 最后利用Mott和Davis提出的非晶材料由非晶到晶态的结构转变模型对结果进行了解释, 并通过薄膜XRD和Raman光谱进一步验证了结构变化是薄膜热致变化的重要原因. 关键词： 20Sb₁₅Se₆₅薄膜')" href="#">Ge₂₀Sb₁₅Se₆₅薄膜 热处理 光学带隙 折射率     

ZnSb掺杂的Ge2Sb2Te5薄膜的相变性能研究

本文采用双靶(ZnSb靶和Ge₂Sb₂Te₅靶)共溅射制备了系列ZnSb掺杂的Ge₂Sb₂Te₅(GST)薄膜. 利用X射线衍射、透射电子显微镜、原位等温/变温电阻测量、X射线光电子能谱等测试研究了薄膜样品的非晶形态、电学及原子成键特性. 利用等温原位电阻测试表明ZnSb掺杂的Ge₂Sb₂Te₅薄膜具有更高的结晶温度. 采用Arrhenius 公式计算发现ZnSb掺杂的Ge₂Sb₂Te₅薄膜的十年数据保持温度均高于传统的Ge₂Sb₂Te₅薄膜的88.9℃. 薄膜在200, 250, 300和350℃ 下退火后的X射线衍射图谱表明ZnSb的掺杂抑制了Ge₂Sb₂Te₅薄膜从fcc态到hex态的转变. 通过对薄膜的光电子能谱和透射电镜分析可知Zn, Sb, Te原子之间键进行重组, 形成Zn–Sb 和Zn–Te 键, 且构成非晶物质存在于晶体周围. 采用相变静态检测仪测试样品的相变行为发现ZnSb掺杂的Ge₂Sb₂Te₅薄膜具有更快的结晶速度. 特别是(ZnSb)_24.3(Ge₂Sb₂Te₅)_75.7薄膜, 其结晶温度达到250℃, 十年数据保持温度达到130.1℃, 并且在70 mW激光脉冲功率下晶化时间仅～64 ns, 远快于传统Ge₂Sb₂Te₅薄膜的晶化时间～280 ns. 以上结果表明(ZnSb)_24.3(Ge₂Sb₂Te₅)_75.7薄膜是一种热稳定性好且结晶速度快的相变存储材料.     

Co1-xNixSb3-ySey热电输运中晶界和点缺陷的耦合散射效应

结合机械合金化与放电等离子烧结工艺制备了Ni和Se共掺的细晶方钴矿化合物Co_1-xNi_xSb_3-ySe_y,研究了晶界和点缺陷的耦合散射效应对CoSb₃热电输运特性的影响.通过Ni掺杂优化载流子浓度提高功率因子.在x=0.1时,功率因子达到最大值1750μWm^-1K^-2(450℃),是没有掺Ni试样的两倍.晶界和点缺陷的耦合散射机理使晶格热导率急剧下降,其中Co_0.9Ni_0.1Sb_2.85Se_0.15的室温晶格热导率降低至1.67Wm^-1K^-1,接近目前单填充效应所能达到的最低值1.6Wm^-1K^-1,其热电优值ZT在450℃时达到最大值0.53.将Callaway-Von Baeyer点缺陷散射模型嵌入到Nan-Birringer有效介质理论模型,对晶界散射和点缺陷散射的耦合效应对热导率的影响进行了定量分析,模型计算与实验结果符合.理论模型计算表明,当晶粒尺寸下降到50nm同时掺杂引入点缺陷散射后,Co_0.9Ni_0.1Sb_2.85Se_0.15的晶格热导率下降到0.8Wm^-1K^-1. 关键词： 3')" href="#">CoSb₃ Ni和Se掺杂 热电性能 耦合散射效应     

硫系非晶半导体薄膜中的超快光 Kerr效应

利用飞秒激光超外差光Kerr(OHD-OKE)技术研究了As₂S₃, As₂Se₃, GeS₂, GeSe₂, Ge₂₀As₂₅S₅₅, Ge₂₀As₂₅Se₅₅, Ge₁₀As₄₀S_{20关键词： 全光开关 硫系非晶半导体薄膜 飞秒激光超外差光Kerr(OHD-OKE) 三阶非线性}     

Homopolar bonds in Se-rich Ge-As-Se chalcogenide glasses

We have prepared three groups of Ge–As–Se glasses in which the Se content is 5.5 mol%, 10 mol%, and 20 mol%rich, respectively. We explored the possibility of suppressing the formation of the Ge–Ge and As–As homopolar bonds in the glasses. Thermal kinetics analysis indicated that the 5.5 mol% Se-rich Ge_(11.5)As_(24)Se_(64.5) glass exhibits the minimum fragility and thus is most stable against structural relaxation. Analysis of the Raman spectra of the glasses indicated that the Ge–Ge and As–As homopolar bonds could be almost completely suppressed in 20 mol% Se-rich Ge_(15)As_(14)Se_(71) glass.     

First-principles calculations of nitrogen-doped antimony triselenide: A prospective material for solar cells and infrared optoelectronic devices

This study is focused on calculation of the electronic structure and optical properties of non-metal doped Sb2Se3 using the first-principles method. One and two N atoms are introduced to Sb and Se sites in a Sb₂Se₃ crystal. When one and two N atoms are introduced into the Sb₂Se₃ lattice at Sb sites, the electronic structure shows that the doping significantly modifies the bandgap of Sb₂Se₃ from 1.11 eV to 0.787 and 0.685 eV, respectively. When N atoms are introduced to Se sites, the material shows a metallic behavior. The static dielectric constants ε1(0) for Sb₁₆Se₂₄, Sb₁₅N₁Se₂₄, Sb₁₄N₂Se₂₄, Sb₁₆Se₂₃N₁, and Sb₁₆Se₂₂N₂ are 14.84, 15.54, 15.02, 18.9, and 39.29, respectively. The calculated values of the refractive index n(0) for Sb₁₆Se₂₄, Sb₁₅N₁Se₂₄, Sb₁₄N₂Se₂₄, Sb₁₆Se₂₃N₁, and Sb₁₆Se₂₂N₂ are 3.83, 3.92, 3.86, 4.33, and 6.21, respectively. The optical absorbance and optical conductivity curves of the crystal for N-doping at Sb sites show a significant redshift towards the short-wave infrared spectral region as compared to N-doping at Se sites. The modulation of the static refractive index and static dielectric constant is mainly dependent on the doping level. The optical properties and bandgap narrowing effect suggest that the N-doped Sb₂Se₃is a promising new semiconductor and can be a replacement for GaSb due to its very similar bandgap and low cost.     

Linear optical characterization of chalcogenide glasses

A simple experimental method is used to obtain the evolution of both the refractive index and the linear absorption coefficient as a function of the optical wavelength in the near infrared range (from 900 up to 1700 nm with 10 nm resolution). Several chalcogenide glasses (As₂S₃, As₂Se₃, GeSe₄) are tested and the corresponding Cauchy coefficients are determined. Comparison of our results shows a good agreement with values available in the literature at some wavelength. Application of this method is used to estimate Cauchy coefficients of Ge₁₀As₁₀Se₈₀ for the first time to our best knowledge.     

Na_2Ge_2Se_5电子结构和光学性质的第一性原理研究

Na_2Ge_2Se_5是一种优异的红外非线性晶体材料.采用基于第一性原理的密度泛函理论赝势平面波方法对Na_2Ge_2Se_5进行结构优化,并以此为基础计算研究了Na_2Ge_2Se_5的电子结构和光学性质.结果表明:Na2Ge2Se5是宽禁带间接带隙半导体,价带至导带的电子跃迁主要来自于Ge和Se的48,4p态;Na对光学性质的贡献较小,Ge和Se之间的相互耦合作用决定了Na_2Ge_2Se_5的光学性质;该晶体在紫外区有强烈的反射和吸收,静态折射率为2.133,双折射率值适中,为0.145.理论计算结果表明,Na_2Ge_2Se_5是一种性能优良的红外非线性光学晶体材料.     

Ionic diffusion and local hopping in copper chalcohalide glasses measured using Cu tracer and I-Mössbauer spectroscopy

For the first time, ⁶⁴Cu tracer measurements of ionic diffusion were performed for several copper-rich glass compositions in the CuI---As₂Se₃, CuI---SbI₃---As₂Se₃, CuI---PbI₂---As₂Se₃, CuI---PbI₂---SbI₃---As₂Se₃ and Cu₂Se---As₂Se₃ systems. In accordance with previous a.c. impedance results and Wagner d.c. polarization measurements, it was found that pure Cu⁺ ion-conducting glasses (50CuI---17PbI₂---33As₂Se₃ and 50CuI---20PbI₂---10SbI₃---20As₂Se₃) exhibit the highest copper tracer diffusion coefficients, D_Cu, and the lowest diffusion activation energies. The values of D_Cu at room temperature are higher by 4.5–5.5 orders of magnitude than those in an As₂Se₃ glass. The Haven ratio, H_R, is found to be 0.52–0.61 (ternary glass) and 0.93–1.00 (quaternary glass). Short-range diffusional displacements of the iodide ions induced by the hopping Cu⁺ ions are also detected in the CuI---PbI₂---SbI₃---As₂Se₃ glassy system using ¹²⁹I-Mössbauer spectroscopy in the temperature range of 4.2 to 305 K. The activation energy of local hopping, E_h ≈ 0.31 eV, is very similar to that of bulk ionic conductivity (0.37 eV) and copper diffusion (≈ 0.33 eV). In contrast to CuI-based vitreous alloys, 50Cu₂Se---50As₂Se₃ glass exhibits D_Cu that are two to five orders of magnitude lower, and the copper ion transport number, t_Cu⁺, is between 10⁻³ and 10⁻⁴ in the temperature range 140–170 °C.     

Magnetic and transport properties of some U3T3X4-compounds (T = Co, Ni, Cu and X = Sb, Sn)

We have prepared and studied a new series of isostructural U₃T₃X₄-compounds with T = Co, Ni, Cu for X = Sb and T = Ni for X = Sn. Ferromagnetism is found for U₃Co₃Sb₄ and U₃Cu₃Sb₄ below 10 and 88 K, respectively. In contrast, no magnetic order was observed down to 1.7 K for the semiconductor U₃Ni₃Sb₄ and the “moderately” heavy-fermion system U₃Ni₃Sb₄.     

Structure and optical properties of GeGaS films deposited by thermal evaporation

Amorphous GeGaS thin films have been successfully deposited onto glass slides at room temperature by the thermal evaporation technique. The structural units of the films were studied using Raman spectroscopy. In addition to the basic structural units of GeS₄ tetrahedra, there are some SS and GeGe homopolar bonds which exist in the films. The increase in Ge atoms leads to the replacement of SS bonds by GeGe bonds, and the isolated Ge(Ga)S₄ tetrahedra units transform into corner-sharing or edge-sharing Ge(Ga)S₄ tetrahedra units in the films. The refractive index and optical band gap were derived from transmission spectra of films. The values of optical band gap decrease while the refractive indices increase with increasing Ge content. Composition dependence of optical band gap and refractive index has also been interpreted in terms of the variation in the structure of films based on Raman spectra.     

Study on the structure dependent ultrafast third-order optical nonlinearity of GeS2–In2S3 chalcogenide glasses

The results of the femtosecond time-resolved optical Kerr at 820 nm in GeS₂–In₂S₃ chalcogenide glasses indicate that the response time in GeS₂–In₂S₃ glasses is subpicosecond, which is predominantly due to the distortion of the electron cloud. The value of χ⁽³⁾ in 0.95GeS₂–0.05In₂S₃ glass is also as large as 2.7 × 10⁻¹³ esu, and it reduces with the addition of In₂S₃, which may be ascribed to the microstructure evolution of GeS₂–In₂S₃ glasses. It is deduced that the intrinsic [Ge(In)S₄] tetrahedral structure units that possess the high hyperpolarizability may do great contribution to the enhancement of third-order optical nonlinearity while [S₃Ge–GeS₃] ethane-like molecular units make no considerable contribution to that in femtosecond time scale. These GeS₂–In₂S₃ and GeS₂–In₂S₃-based chalcogenide glasses would be expected to be the promising materials for all-optical switching devices.