SmxLa1-xP5O14和DyxY1-xP5O14晶体的荧光寿命研究

本文用脉冲衰减法和时间分辨荧光光谱法测量了六种不同稀土离子浓度的SmxLa1-xP5O4晶体的4G5/2→6HJ(J=5/2,7/2,9/2,11/2)四个能级和七种不同稀土离子浓度的DyxY1-xP5O14晶体的4F9/2→6HJ(J=15/2,13/2,11/2,9/2)四个能级的荧光寿命和荧光强度。结果指出,在这类晶体中,Sm3+和Dy3+的荧光寿命随着离子的浓度增加而变短,存在着严重的荧光浓度猝灭现象。最后还讨论了浓度与寿命,寿命与荧光强度的关系。     

PECVDSi3N4/InP界面特性的研究

本文利用Auger分析技术和C-V测量方法,详细地研究了PECVDSi₃N₄/InP界面特性,Auger能谱分析表明热处理使界面面发生互扩散,同时InP的热分解导致P元素穿过Si₃N₄薄膜到达表面。C-V测量表明Ag/Si₃N₄/InPMIS结构可以实现载流子的堆积、耗尽和反型。     

第Ⅱ种强度不等的两态叠加多模叠加态光场的等阶N次方H压缩1腔模总数与压缩阶数两者之积取偶数的情形

利用多模压缩态理论研究了第种强度不等的非对称两态叠加多模叠加态光场|Ψ_Ⅱ^(ab)〉q的等阶N次方H压缩特性.结果发现:1)当腔模总数q与压缩阶数N的乘积取偶数,亦即qN=2p时,无论p=2m(m=1,2,3,…,…),还是p=2m+1(m=0,1,2,3,…,…),只要各模的初始相位差(φ_j^(a)-φ_j^(b))、态间的初始相位差(θ_nq^(aR)-θ_nq^(bR))及光子干涉项的幅度 1R_j^(a)R_j^(b)等分别满足一定的条件,则态|Ψ_||^(ab)〉q的第一和第二正交分量总可分别呈现出周期性变化的等阶N次方H压缩效应.2)当qN=2p且p=2m+1(m=0,1,2,3,…,…)时,若构成态|Ψ_Ⅱ^(ab)〉q的两个不同的量子光场态中各对应模的强度(即平均光子数)和初始相位相等,亦即R_j^(a)=R_j^(b)和φ_j^(a)=φ_j^(b)(j=1,2,3,…,q),则态|Ψ_Ⅱ^(ab)〉q可呈现出“等阶N次方H压缩简并”现象.     

抗癌药物铂络合物构效关系的物理方法研究

本文用X射线衍射、傅里叶变换红外光谱、差热分析等物理方法研究了抗癌药物铂络合物特性、结构以及构效关系。研究结果表明:cis-[Pt(NH₃)₂Cl₂]属简单斜方晶系,晶格常数a=0.9221nm,b=0.8771nm,c=0.6890nm.草酸二氨合铂的结构为斜方晶系,其晶格常数为:a₁=1.0721nm,a₂=0.6402nm,a₃=1.8570nm,并用傅里叶变换红外光谱、差热分析、元素分析等方法对它们理化特性进行了研究.     

利用激光溅射原子束装置结合时间切片速度成像技术对于金属态-态反应动力学的相关研究

利用新建激光溅射交叉分子束装置,结合时间切片速度成像技术开展了金属原子态-态反应动力学的相关研究. 超声金属原子束是由激光溅射金属棒产生,结合无气体溢流通道的自由扩散设计,得到了质量很好的金属原子超声束. 本文选择Al+O₂反应体系来测试新建金属交叉分子束实验装置的性能. 通过(1+1) 共振多光子电离技术,以AlO(D²∑⁺)为中间态来探测特定转动态的产物AlO自由基. 相同波长下可以同时得到反应产物AlO(X²∑⁺,v=0,N和N+14)两个转动态的速度成像,分别对应着Δv=1的P(N)和R(N+14)跃迁. 在244.145 nm同时探测到P(15)和R(29)的跃迁,形成的两个环在切片成像图中可以完全区分开,这两个跃迁分别对应着反应产物AlO(v=0,N=15)和AlO(v=0,N=29)两个转动态. 对应此两个转动态的能级差为403 cm^-1. 这两个反应产物转动态的区分表明了该实验装置与最近的一篇研究报道[J. Chem. Phys. 140, 214304 (2014)]相比较,具有较好的碰撞能量分辨率.     

多通道声光偏转选址开关

本文报道1×N多通道声光偏转选址开关的研究.由 Ti 扩散 LiNbO₃波导上两个短程透镜和一个倾斜 chirp 叉指换能器构成的集成光学声光偏转器,在两端分别对接一根和N根单模光纤时,用作多通道选址开关,在换能器带宽为200MHz,对1.3μm波长,可实现N=24;带宽增加到500MHz,可达到N=64,在波长为0.633μm的 He-Ne 激光下进行的实验和理论符合.     

Sn-based type-VIII single-crystal clathrates with a large figure of merit

Single-crystal samples of type-VIII Ba₈Ga_{16 - x}Cu_xSn₃₀ (x=0, 0.03, 0.06, 0.15) clathrates were prepared using the Sn-flux method. At room temperature the carrier density, n, is 3.5-5×10¹⁹ cm^-3 for all the samples, the carrier mobility, μ_H, increases to more than twice that of Ba₈Ga₁₆Sn₃₀ for all the Cu doping samples, and consequently the electrical conductivity is enhanced distinctly from 1.90×10⁴ S/m to 4.40×10⁴ S/m, with the Cu composition increasing from x=0 to x=0.15. The Seebeck coefficient, α , decreases slightly with the increases in Cu composition. The κ values are about 0.72 W/mK at 300 K and are almost invariant with temperature up to 500 K for the samples with x=0 and x=0.03. The lattice thermal conductivity, κ_L, decreases from 0.59 W/mK for x=0 to 0.50 W/mK for x=0.03 at 300 K. The figure of merit for x=0.03 reaches 1.35 at 540 K.     

Zn在Ga1-xAlxAs中的扩散规律

本文论述了在720℃～750℃的温度下,Zn在Ga1-xAlxAs,GaAs中的扩散。研究了结深x1,随片子表面Al组份x值的变化规律。实验表明在同一扩散条件下,Ga1-xAlxAs与GaAs两种材料的结深xj并不相同。在此基础上获得了Al组份x=0.34的最佳扩散条件。     

金、铜、铂、银表面光学二次谐波参数的研究

以1.06μm激光为基频光,测量了金、铜、铂、银膜的反射二次谐波随基频光偏振角的变化,在b=-1的条件下拟合求得了这几种样品面谐波电流的唯象参数“a”值。     

多声子跃迁的Franck-Condon因子

在位形座标中,表示电子态u和v的两条抛物线水平方向位移(2S)1/2,垂直方向位移pohω。选取横座标(无量纲位形z)单位,使极小值位于原点的抛物线在z=±1处纵座标为0点振动能1/2hω。S即黄-李-Пеяар因子。     

MOCVD-GaxIn1-xAsyP1-y/InPDBR结构的晶格振动

利用微区Raman散射技术研究了MOCVD-Ga_xIn_1-xAs_yP_1-y/InPDBRs结构的晶格振动。在InP衬底上生长的与InP晶格匹配的四元合金Ga_0.4In_0.6As_0.85P_0.15中包含三种主要的振动模式,分别归属于类InAs、类GaAs和类GaInP。随着Ga_0.4In_0.6As_0.85P_0.15与InP交替生长构成的DBRs结构周期数增加,Raman散射谱中三种振动模式的谱线线型发生明显变化,类InAs振动强度不变,谱线窄化,峰值位置向低频方向移动,类GaAs和类GaInP振动强度逐渐减弱。同时类InAs与类GaAs振动强度比增大。Raman散射研究中声子的限制效应表明多层结构生长过程中界面存在非完整晶态。     

硅衬底Ba1-xSrxNbyTi1-yO3薄膜光敏特性的研究

利用硅平面工艺和氩离子束镀膜技术在SiO2/Si衬底上淀积一层厚45nm的钛铌酸锶钡(Ba1-xSrxNbyTi1-yO3)薄膜，制成Al/Ba1-xSrxNbyTi1-yO3/SiO2/Si结构平面型薄膜电阻器。测试了该薄膜电阻器的吸收光谱，不同照度、电压下的光电流，调制光下的频率特性。实验结果表明：在钛酸钡中掺入锶(Sr)和铌(Nb)后，禁带内引入了杂质能级，钛铌酸锶钡禁带宽度变为2.7eV，且可见光区域存在连续的吸收峰。该薄膜在近紫外及可见光范围内具有良好的光敏特性，其灵敏度和光电导增益较高，并且具有较好的线性光照特性。光照强度较低时，电阻器的光照特性属于单分子复合过程；光照强度较高时，电阻器的光照特性属于双分子复合过程。通过对该薄膜电阻器频率特性的测量得出：在光照度为200lx时，薄膜中光生载流子的寿命为27ms。     

微波反射光电导衰减法测少子寿命演示实验

采用微波反射光电导衰减法设计了测试少子寿命的演示实验装置.实验装置主要由脉冲激光源、微波发射接收和数据采集处理系统等部分组成.该实验可以直观地演示非平衡载流子随时间的衰减过程,定量给出少子寿命、扩散系数和扩散长度.     

New results on diffusion lengths measurements in wide bandgap semiconductors, obtained from steady state photocarrier gratings (SSPG)

In this work we develop our previous measurements of diffusion lengths in gallium nitride using the steady-state photocarrier grating (SSPG) method. We show how the use of a monomode HeCd laser as well as a photoelectrical compensation scheme improves significantly the measurement, and demonstrate the ruggedness of the SSPG technique as well as the reliability of the obtained diffusion length, which is typically in the range of several hundreds of nanometers. The small-signal photocurrent decay is exponential, with decay times in the millisecond range, a clear indication of trap-limited dynamics. We use the photocarrier grating field quenching to estimate the majority carrier drift mobility. Finally, a thermalization-limited diffusion mechanism is proposed in order to overcome a serious conflict between the experimental data and the recombination-limited SSPG diffusion theory.     

激光束诱导电流法提取HgCdTe光伏探测器的电子扩散长度

由于得到HgCdTe扩散长度L_p的标准测试结构会损伤p-n结单元,实验中广泛采用激光束诱导电流（LBIC）提取的等效扩散长度L来代替L_p.本文通过二维数值模拟,分析了等效扩散长度L和扩散长度L_p 的关系.二者的比例关系为L/L_p=1.1,该基本关系不受器件的关键参数如掺杂浓度、载流子寿命、载流子迁移率等的影响.最后将激光束 关键词： 碲镉汞 激光束诱导电流 扩散长度     

Laser beam induced current microscopy and photocurrent mapping for junction characterization of infrared photodetectors

For non-destructive optical characterization, laser beam induced current(LBIC) microscopy has been developed into as a quantitative tool to examine individual photodiodes within a large pixel array. Two-dimensional LBIC microscopy, also generally called photocurrent mapping(PC mapping), can provide spatially resolved information about local electrical properties and p-n junction formation in photovoltaic infrared(including visible light) photodetectors from which it is possible to extract material and device parameters such as junction area, junction depth, diffusion length, leakage current position and minority carrier diffusion length etc. This paper presents a comprehensive review of research background, operating principle, fundamental issues, and applications of LBIC or PC mapping.     

Study on the structural characteristics of HgCdTe photodiodes using laser beam-induced current

The structural characteristics of typical n⁺-on-p HgCdTe photodiodes have been studied by laser beam-induced current (LBIC). The dependence of LBIC on laser wavelength, junction depth and localized leakage has been presented. The diffusion length of minority carrier of p-type region is extracted by the exponential decay fitting of the curve of LBIC. It is found that the peak magnitude of LBIC and junction depth approximate to a linear relationship for practical values of device fabrication. The diffusion length monotonously increases with the junction depth. A notable shift of LBIC profile is observed when localized leakage exists. This provides a useful explain for LBIC applying to characterize the structure and process uniformity of HgCdTe infrared detectors.     

Determination of diffusion length of minority carriers in epitaxial layers by photocurrent spectroscopy

We have determined the minority carrier diffusion length in n-type and p-type GaAs epitaxial layers grown on GaAs substrates as well as on intentionally misoriented Si substrates by photocurrent spectroscopy. It is found that for heteroepitaxial GaAs-on-Si, the minority carrier diffusion length is limited by the amount of dislocation density irrespective of the doping level. The value of dislocation density obtained from diffusion length measurements agrees well with that obtained from the double-crystal x-ray diffraction measurements.     

Diluted II-VI oxide semiconductors with multiple band gaps

We report the realization of a new mult-band-gap semiconductor. Zn(1-y)Mn(y)OxTe1-x alloys have been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of extended states located within the band gap of the Zn(1-y)Mn(y)Te host. When only 1.3% of Te atoms are replaced with oxygen in a Zn0.88Mn0.12Te crystal the resulting band structure consists of two direct band gaps with interband transitions at approximately 1.77 and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model. With multiple band gaps that fall within the solar energy spectrum, Zn(1-y)Mn(y)OxTe1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.     

Magnetic-Field-Induced Spin Nematicity in FeSe_(1-x)S_x and FeSe_(1-y)Te_y Superconductor Systems

The angular-dependent magnetoresistance(AMR) of the ab plane is measured on the single crystals of ironchalcogenide FeSe_(1-x)S_x(x=0,0.07,0.13 and 1) and FeSe_(1-y)Te_y(y=0.06,0.61 and 1) at various temperatures under fields up to 9 T.A pronounced twofold-anisotropic carrier-scattering effect is identified by AMR,and attributed to a magnetic-field-induced spin nematicity that emerges from the tetragonal normal-state regime below a characteristic temperature Tsn.This magnetically polarized spin nematicity is found to be ubiquitous in the isoelectronic FeSe_(1-x)S_x and FeSe_(1-y)Te_y systems,no matter whether the sample shows an electronic nematic order at T_s(?)T_(sn),or an antiferromagnetic order at T_N T_(sn),or neither order.Importantly,we find that the induced spin nematicity shows a very different response to sulfur substitution from the spontaneous electronic nematicity:The spin-nematic Tsn is not suppressed but even enhanced by the substitution,whereas the electronicnematic Ts is rapidly suppressed,in the FeSe_(1-x)S_x system.Furthermore,we find that the superconductivity is significantly suppressed with the enhancement of the induced spin nematicity in both FeSe_(1-x)S_x and FeSe_(1-y)Te_y samples.