硫化镉单晶体本征吸收边的类氢光谱系

利用CdS单晶体,一块约厚0.1毫米,另一块约厚0.05毫米,观察它们在天然光及偏振光下的吸收光谱。在室温及液态空气温度下,天然光的吸收指示CdS晶体长波吸收边波长随厚度及温度而改变。在光谱仪狭缝前放一偏振片观察到长波吸收边波长随晶体C轴与偏振光电矢量间介角的改变。 在液态空气温度下观察CdS晶体对偏振光的吸收情况,发现在晶体本徵吸收边出现由七条强而锐的谱线组成的一个类氢光谱系。 测量结果发现每条谱线的波数满足下列公式: v_k=20270-11754/k~2(厘米)~(-1),式内k=3,4,5,…9;k=2的线未在光谱中发现。从此式推出的CdS晶体能级的系限加以温度较正为2.41电子伏,与前人用其他方法所得2.42电子伏是很相近的。激子的等价质量与电子质量之比为4.3。 CdS晶体与ZnS晶体结构相似,常数数值相近,由此可以猜测CdS晶体能级的满带可能是属于S-离子。所观察到的激子光谱类氢系可能是S-离子的激发态。     

极性晶体中极化子效应对界面强耦合激子性质的影响

在Huybrechts关于强耦合极化子的模型基础上,采用LLP变分法研究了极性晶体中激子与IO声子强耦合、与LO声子弱耦合体系的基态能量,推导出了激子的自陷能和诱生势的表达式,并以AgCl/AgBr晶体为例进行了数值计算,结果表明,激子的自陷能不仅与激子的坐标z有关,而且电子-空穴间距离ρ对激子自陷能的影响也十分显著;激子的诱生势不仅与电子-空穴间距离ρ有关,而且激子距离晶体界面的位置z对诱生势的影响也十分显著.     

圆柱状量子点量子导线复合系统的激子能量和电子概率分布

建立了圆柱状量子点量子导线复合系统中激子满足的方程，用微扰论求出激子能量.以CdS/HgS/CdS/HgS/CdS圆柱状量子点量子导线复合系统为例，研究了系统中电子的概率分布和系统线度对激子能量的影响.结果表明：系统中电子、空穴以及激子的能量均随量子点高度h₀的增大而减小，电子-空穴相互作用对基态激子能量的影响要大于激发态；电子沿径向方向的概率分布呈起伏状，在轴线和表面附近的概率趋于零，而在R/2附近概率最大；在量子点附近电子沿轴向方向的概率分布呈振荡特征 关键词： 量子点 量子导线 激子 能量     

极性晶体膜中强耦合激子的极化子效应和温度依赖性

采用线性组合算符和变分方法研究了极性晶体膜中激子与表面光学（SO）声子强耦合、与体纵光学（LO）声子弱耦合体系的性质,推导出了激子诱生势的表达式,并以AgBr晶体为例进行了数值计算.结果表明：激子的诱生势不仅与电子-空穴间距离有关,而且温度与极性晶体膜厚度对激子诱生势的影响也十分显著.     

极性晶体膜中强耦合激子的极化子效应和温度依赖性

采用线性组合算符和变分方法研究了极性晶体膜中激子与表面光学(SO)声子强耦合、与体纵光学(LO)声子弱耦合体系的性质,推导出了激子诱生势的表达式,并以AgBr晶体为例进行了数值计算.结果表明:激子的诱生势不仅与电子-空穴间距离有关,而且温度与极性晶体膜厚度对激子诱生势的影响也十分显著.     

纳米CdS-磺化聚苯胺（SPAn）多层复合膜的光学特性研究

研究了利用层-层自组织生长法制备的磺化聚苯胺-CdS纳米晶体复合膜的光学特性.研究发现，随样品中CdS 纳米晶体尺寸的减小，量子尺寸效应明显增强；在紫外吸收谱中表现为吸收边出现了明显蓝移；在光致发光谱中，不仅激子直接复合产生的带边发射产生了蓝移，而且陷阱态复合产生的宽带发射也发生了蓝移.还发现样品经低温退火处理后，激子复合产生的带边发射显著增强，发射带宽随纳米尺寸的减小而变窄.这说明退火后CdS 纳米晶粒的有序性和均匀度显著增加. 关键词： CdS 纳米晶体 SPAn 吸收 发光     

极性晶体膜中强耦合激子的性质

在强耦合极化子模型基础上,采用Lee-Low-Pines(LLP)变分法研究了极性晶体膜中激子与表面光学(SO)声子强耦合、与体纵光学(LO)声子弱耦合体系的性质.讨论了极性晶体膜中激子的诱生势与膜厚度和温度的变化关系.结果表明:激子的诱生势不仅与电子-空穴间距离有关,而且与极性晶体膜厚度有关,同时温度对激子诱生势的影响十分显著.     

高密度激发下CdS单晶的自由激子发光

本文首次在77K温度的电致发光光谱上,观测到了自由激子和自由激子(Ex-Ex)散射的发射带P。根据半经典理论,得到CdS单晶在高激发密度下的激子有效温度高于晶格温度。并且在77K温度下,通过氮分子激光器3371Å谱线的激发,观察到了Ex-Ex散射的P带的受激发射现象。     

CdTe/CdS核壳结构量子点超快载流子动力学

在水相合成CdTe以及CdTe/CdS核壳结构量子点基础上, 利用基于抽运-探测技术的瞬态差分透射技术研究了CdTe量子点以及不同CdS壳层厚度的CdTe/CdS量子点的最低激子能态的超快激发与弛豫动力学. 研究表明:相比于CdTe,CdTe/CdS量子点的电子空穴由于空间分离,其所需的激发时间要长于电子空穴空间重叠态所需要的激发时间.随着壳层厚度的增加, 量子点表面的钝化有效地减少了表面态相关弛豫机理,并延长相对应的弛豫时间.     

正向高密度脉冲电流激发下ZnSe MIS二极管中的自由激子发光

本文测量了在77K和正向脉冲电流密度为50～500mA/mm2的激发下,ZnSe MIS二极管的电致发光光谱.首次在高电流密度激发下的ZnSe晶体的电致发光光谱上,观测到自由激子与自由激子间(Ex-Ex)的散射.本中根据自由激子的动能分布,讨论了2LO声子协助的自由激子伴线的形状,发现当激发电流密度增高时,自由激子的有效温度大于晶格温度,这可归结为激子与激子间的非弹性散射.     

CdS／SiO_2半导体玻璃复合材料的低频Raman散射光谱研究

ＣｄＳ／ＳｉＯ＿２半导体玻璃复合材料的低频Ｒａｍａｎ散射光谱研究王凯旋，隗罡，黄建滨，戴庆红，赵壁英，桂琳琳，谢有畅，唐有祺（北京大学物理化学研究所北京１００８７１）ＡＳｔｕｄｙｏｆＣｄＳＳｅｍｉｅｏｎｄｕｃｔｏｒｉｎＳｉｌｉｃａＧｌａｓｓｅｓｂｙＬ...     

Theoretical Treatment of the Hyper-Raman Scattering of Light Under Two-Photon Excitation Near the Lowest Exciton Level in a CdS Crystal

Journal of Russian Laser Research - We theoretically study the resonant hyper-Raman scattering of light by LO-phonons in a CdS crystal with the wurtzite structure, taking into account the influence...     

Surface enhanced Raman scattering by CdS quantum dots

Surface enhanced Raman scattering is studied in nanostructures with CdS quantum dots formed using the Langmuir-Blodgett technology. Features due to quantum dot longitudinal optical phonons are observed in the Raman spectra of both free CdS quantum dots and such dots distributed in an organic matrix. The surface enhanced Raman scattering by nanostructures with CdS quantum dots covered by an Ag cluster film is observed experimentally. Applying Ag clusters onto the nanostructure surfaces results in a sharp (40-fold) increase in the intensity of Raman scattering by optical phonons in the quantum dots. It is shown that the dependence of surface enhanced Raman scattering on the excitation energy is resonant with a maximum at the energy corresponding to the maximum absorption coefficient of Ag clusters.     

Brillouin scattering of “forbidden” polaritons in CdS

We use the results of Mahan and Hopfield's analysis of the B-exciton in CdS to derive the dispersion relations for three excitonic-polariton branches. Two of these polaritons are well known and have been investigated experimentally for the A-exciton in CdS by Winterling and Koteles. The third polariton is normally optically inactive but becomes allowed due to spin-orbit interaction which lifts the spin degeneracy of the exciton by an amount, øk, where k is the crystal momentum and ø is a coupling constant. We calculate the energy loss due to Brillouin scattering of polaritons between allowed and forbidden branches and predict that this loss should be experimentally observable. If seen, the value of ø could be more accurately determined and Mahan and Hopfield's conjectured model would be decisively confirmed.     

Monte Carlo simulation of light scattering from size distributed sub-micron spherical CdS particles in a volume element

Simulation of polarized light scattering by spherical particles having modal radius of 180 nm is presented in this paper. A Monte Carlo method which is based on the Stokes-Mueller formalism developed in ANSI Standard C-language is used for simulation. Single scattering is considered in our program with monodispersed sub-micron sized spherical CdS particles. We have considered only θ dependent scattering as described by Mie theory for spherical CdS particles. The experiments for studying light scattering properties of these particles were conducted in a designed and developed laser based light scattering studies setup. The simulation results were compared with experimental results and theoretical results obtained purely from Mie theory. The closeness of agreement or disagreement between these results is discussed in this paper.     

The role of frenkel excitons in low-energy electron interaction with molecular adfilms

The problem of the interaction of low-energy electrons with molecular films near a solid is discussed. It is shown that, as a result of the electron-metal interaction, the new “nonelastic” channel of electron-exciton complex decay is possible, during which the electron-exciton pair dissociates and the electron transmits into the metal. We have analysed the possible shapes of the resonance features observed in the experiments on the transmission and the reflection of the low-energy electrons from the surface of a solid covered by a monolayer molecular film.     

Estimation of Velocities and Energy Densities of GHz Domain Shear Fluxes Propagating in Sapphire by Brillouin Scattering Technique

Energy densities and velocities of GHz domain shear fluxes in sapphire were estimated using the Brillouin scattering theory. The Brillouin scattering cross section was calculated from sapphire’s material parameters. The experiment was done using CdS domain shear fluxes. Direct contact was used to mirror surfaces of the CdS and the sapphire. Injection efficiency of shear fluxes ranging from 0.2 GHz to 1.1 GHz into the sapphire from CdS was measured by this method. In addition, energy density distributions of domain fluxes in the sapphire were estimated from scattering light intensities by employing the scattering cross section of the sapphire.     

用一维光子带隙结构增强硫化镉双光子吸收研究

用真空镀膜方法制备了含有单个CdS缺陷层的具有不同周期和结构参量的TiO2／SiO2一维光子晶体。用抽运一探测技术研究了CdS缺陷层的双光子吸收（TPA）现象。实验结果表明：一维光子晶体中CdS缺陷层的双光子吸收显著增强。不同周期和结构参量的一维光子晶体中CdS缺陷层的双光子吸收系数不同。双光子吸收的增强来源于由光局域化导致的缺陷层的电场强度的增加。缺陷层电场强度与一维光子晶体的结构有关,如周期,光子带隙的位置与宽度及缺陷模式等因素都会影响缺陷层电场强度。采用四分之一波长的高低折射率介质层和与入射波长匹配的缺陷模可以得到最大的缺陷层电场强度。     

Temperature-dependent polarization of resonance Raman scattering in CdS

Temperature-dependent polarization of the 4658 Å—3LO Raman line was studied together with that of the 4727 Å—2LO Raman line in resonance Raman scattering (RRS) in CdS. Temperature-dependent polarization is strongly related to the A-exciton in CdS as a resonant intermediate state. Experimental results are well understood when RRS around the A-exciton is considered as the inelastic scattering of exciton—polaritons by LO phonons.