InGaAs/GaAs单量子阱PL谱的温度变化特性

采用分子束外延方法制备了InGaAs/GaAs单量子阱,利用自组装的光致荧光探测系统,对其进行了光致荧光谱研究。考察了不同温度下荧光峰波长、峰形的影响。研究结果表明:高温时荧光主要是源于带—带间载流子跃迁,而在低温时则来源于束缚在量子阱中激子的跃迁。     

不同厚度CdSe阱层的表面上自组织CdSe量子点的发光性质

利用变温和变激发功率分别研究了不同厚度CdSe阱层的自组织CdSe量子点的发光。稳态变温光谱表明:低温下CdSe量子阱有很强的发光,高温猝灭,而其表面上的量子点发光可持续到室温,原因归结于量子点的三维量子尺寸限制效应;变激发功率光谱表明:量子点激子发光是典型的自由激子发光,且在功率增加时。宽阱层表面上的CdSe量子点有明显的带填充效应。通过比较不同CdSe阱层厚度的样品的发光,发现其表面上量子点的发光差异较大,这可以归结为阱层厚度不同导致应变弛豫的程度不同,直接决定了所形成量子点的大小与空间分布^[1]。     

ZnCdSe量子阱/CdSe量子点耦合结构中的激子隧穿过程

用室温光致发光谱和飞秒脉冲抽运探测方法对不同垒宽的ZnCdSe量子阱/ZnSe/CdSe 量子点新型耦合结构中激子隧穿过程进行研究，观察到激子从量子阱到量子点的快速隧穿过 程.在ZnSe垒宽为10nm, 15nm, 20nm时，测得激子隧穿时间分别为1.8ps, 4.4ps, 39ps. 关键词： ZnCdSe量子阱 CdSe量子点 激子 隧穿     

基质敏化的Er0.1Gd0.9VO4晶体的红外量子剪裁

研究了Er_0.1Gd_0.9VO₄晶体材料的红外量子剪裁现象, 发现了较为有趣的基质敏化的红外量子剪裁现象. 即对于1537.5 nm的⁴I_13/2→⁴I_15/2红外荧光的激发谱存在一个宽而强的337.0 nm波长的激发谱峰,仔细分析可以认定337.0 nm的激发峰对应着基质GdVO₄材料的吸收. 同时,发光谱的测量显示337.0 nm光激发Er_0.1Gd_0.9VO₄材料的基质吸收带时导致的1537.5 nm⁴I_13/2→⁴I_15/2红外荧光的积分强度比其他所有荧光的积分强度的总和大了接近10倍, 它的红外量子剪裁效率仅次于最强的²H_11/2能级受激的红外量子剪裁效率且比其他能级都强. 关键词： 红外的量子剪裁 太阳能电池 0.1Gd_0.9VO₄晶体材料')" href="#">Er_0.1Gd_0.9VO₄晶体材料     

MBE生长PbSe/PbSrSe量子阱结构的光致中红外发光的研究

研究了分子束外延技术生长的PbSe/PbSrSe多量子阱结构的中红外光致荧光现象.高分辨率X射线衍射（HRXRD）谱观察到了多量子阱所特有的多级卫星峰,表明量子阱界面陡峭.变温光致荧光谱测量显示量子阱结构对电子空穴有强的限制效应,在相同温度下,量子阱样品的荧光峰峰位相对PbSe体材料有一定的蓝移.发现量子阱样品的荧光强度同温度有关,温度从150 K上升到230 K时,荧光强度逐渐增大,温度继续升高,荧光强度缓慢下降,但在高于室温时,仍能观察到较强的荧光发射,这说明该量子阱结构材料具有应用于室温工作的中红外 关键词： PbSe/PbSrSe多层量子阱（MQWs） 光致中红外荧光 高分辨X射线衍射（HRXRD）     

低压-MOCVD方法制备CdS-ZnS应变多量子阱

本文报道了用低压(LP)-MOCVD方法制备CdS-ZnS应变多量子阱结构.通过X-射线衍射谱证实了所制备的样品具有比较好的多层结构,并通过77K下的光致发光(PL)光谱,观测到了大的垒层对电子的限制效应及由大的应变引起的阱层带边变化所导致的发光峰蓝移.     

采用MBE生长1.6～2.3μm InGaAsSb/AIGaAsSb多量子阱

采用分子束外延生长了不同In组分的InGaAsSb/AlGaAsSb多量子阱材料.X射线衍射发现量子阱材料有多级衍射卫星峰出现,表明量子阱的界面均匀性和质量较好.研究了不同In组分与光致发光波长的关系,光荧光谱测试表明.所制备的不同In组分的InGaAsSb/AlGaAsSb多量子阱材料,在室温下的发光波长可以覆盖1....     

CBP/Alq3有机量子阱结构的光致发光

采用多源有机分子气相沉积系统(OMBD)制备了CBP/Alq₃有机多量子阱结构,利用电化学循环伏安特性和吸收光谱、小角X射线衍射、荧光光谱研究了量子阱的能带、结构和光致发光的特性。电化学循环伏安特性和吸收光谱的测量结果表明,CBP的最低占据分子轨道(LUMO)与最高占据分子轨道(HOMO)的位置分别为-2.74,-6.00eV,Alq₃的LUMO与HOMO的位置分别为-3.10,-5.80eV,所以CBP/Alq₃有机量子阱为Ⅰ型量子阱结构。小角X衍射测量显示,在小角的位置(2θ的范围在0°～3°)观察到了对应于量子阱结构的多级布拉格衍射峰,表明多层量子阱结构是有序的层状结构,界面比较完整,界面质量比较好。荧光光谱的研究结果表明,Ⅰ型量子阱结构可以有效地把能量从垒层传递给阱层,从而增强了阱层材料的发光。阱层的厚度对发光峰的位置影响很大,随阱层厚度减小,阱层材料的发光峰出现蓝移现象。并对引起发光峰蓝移的原因进行了讨论。     

CdSe/CdMnSe多量子阱的激子光学性质的研究

用分子束外延在GaAs衬底上生长了CdSe/CdMnSe多量子阱结构.利用X射线衍射(XRD)、变密度激发的PL光谱、变温度PL光谱和变密度激发的ps时间分辨光谱研究了CdSe/CdMnSe多量子阱结构和激子复合特性.讨论了随温度升高辐射线宽展宽和辐射复合效率降低的机理.发现不同激发密度下发光衰减时间不同,认为它的机理可能是无辐射复合引起的.在该材料中观测到激子激子散射发射峰,它被变密度激发和变温度PL光谱所证实. 关键词： CdSe/CdMnSe 量子阱 光学性质     

ZnS/CdS/ZnS量子点量子阱的荧光衰减

采用反胶束方法制备了ZnS/CdS/ZnS量子点量子阱，并对其光谱性质进行了研究。结果表明所制得的量子点量子阱尺寸分布均匀，平均粒径为4.5nm，发光峰位于515nm左右，归属于CdS体内的施主－受主对复合。ZnS/CdS/ZnS量子点量子阱中CdS的发光比核－壳结构的ZnS/CdS量子点增强了近四倍，荧光寿命也有所增长。     

Core-shell structure and quantum effect of CdSe/HgSe/CdSe quantum dot quantum well

Core-shell structure CdSe/HgSe/CdSe quantum dot quantum well (QDQW) nanocrystals were firstly synthesized and well controlled by colloidal chemical methods. High-resolution transmission electron microscope (HRTEM) photographs show that the CdSe core has a wurtzite crystal structure and the shell of HgSe has a hexagonal structure. The enhancement and blue shift of photoluminescence (PL) peak was observed which was attributed to the quantum confinement effect of carriers in the HgSe well.     

Parameter-dependent photon echo induced in CdSe/ZnS quantum dot quantum well

The two pulse photon echo (2PPE) phenomena induced by the 1s-1s electronic transition in CdSe/ZnS quantum dot quantum well (QDQW) has been studied by employing semiconductor Bloch equations. The energy eigenvalues and eigenfunctions of electrons and holes have been obtained by solving the stationary Schrödinger equation under effective-mass approximation. The Coulomb interaction, which changes with the size variation of QDQW, has been calculated and analyzed as a perturbation. The variations of the electric transition dipole moment and the energy interval with the changing of the size and structure of the QDQW have also been obtained. It has been shown from the numerical calculation results that the efficiency of 2PPE can be controlled by the variation of the size and structure of the QDQW and the mechanism has been explained in terms of the quantum size confined effect (QSCE) theory.     

Well width‐dependent electron Raman scattering in ZnS/CdSe cylindrical quantum dot quantum well

Electron Raman scattering (ERS) is investigated in ZnS/CdSe cylindrical quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. Different scattering configurations are discussed and the selection rules for the processes are also studied. Singularities in the spectrum are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems. Copyright © 2008 John Wiley & Sons, Ltd.     

Parameter-dependent third-order optical nonlinearity in a CdSe/ZnS quantum dot quantum well in the vicinity of a gold nanoparticle

The nonlinear optical properties of the CdSe/ZnS quantum dot quantum well (QDQW) in the vicinity of a spherical metal nano-particle (MNP) have been described. The third-order nonlinear optical susceptibility induced by the transition between E₁ (inside the well) and E₂ (outside the well) has been calculated for the third-harmonic generation (THG) under the effective mass approximation and modified by the local field theory. The parameters-dependent third-order nonlinear optical susceptibility for the THG has been specifically explored and the influence of the distance between the QDQW and the MNP on the third-order susceptibility for the THG in the system has been shown and analyzed.     

Characteristics of degenerated four wave mixing in ZnS/CdSe/ZnS quantum dot quantum well with multi-shell structure

The wave functions and eigenenergies of electrons in ZnS/CdSe/ZnS cylindrical quantum dot quantum well (QDQW) have been calculated by solving a three-dimensional nonlinear Schrödinger equation, in the framework of the effective-mass envelope-function theory. The third-order susceptibilities of the degenerated four waves mixing (DFWM) have been calculated theoretically by means of compact density matrix. The third-order susceptibilities as the function of the shell radius R₂, R₃ have been analyzed. The results show that the magnitude of nonlinear susceptibility is increased with the increasing of well radius. The resonance frequency of the photon have a shift when R₂ or R₃ is increasing and the relation between nonlinear susceptibility and relaxation time has also been studied.     

Investigation of the radiative lifetime in core–shell CdSe/ZnS and CdSe/ZnSe quantum dots

Using the one band effective mass approximation model we computed the optical properties of the spherical shaped CdSe/ZnS and Cdse/ZnSe core–shell quantum dot (CSQD). For each structure we calculated the charge carrier energies and corresponding wave functions. We investigated the dependence of the carrier energies on various parameters of the CSQD, including its size. Then we calculated the radiative recombination lifetime for the two types of CSQDs nanocrystals. We found that as the size of the dot is increased the optical gap of CSQD is reduced, resulting in a reduction in electron energies and an increase in hole energies. We have shown that the radiative recombination lifetime in the CdSe/ZnS and CdSe/ZnSe CSQDs decreased by increasing the shell thickness around the core of the QD. We also showed that the radiative lifetime in the CdSe/ZnS is less than that in the CdSe/ZnSe CSQDs and is sensitive to the size and nature of shell of the semiconductor's material.     

胶体CdSe量子点的色度学特性研究

使用化学胶体法合成了CdSe量子点，研究了样品的荧光量子产率，发现随CdSe量子点粒径的增大，荧光量子产率存在先增大后减小的现象.研究了CdSe量子点的色度学特性，通过对不同尺寸、不同粒径分布范围的CdSe量子点色度坐标的计算，讨论了粒径分布范围对其荧光颜色饱和度的影响，解释了为何难以获得高颜色饱和度的绿光量子点.利用红、蓝两种不同尺寸的量子点配制出白光样品，提出了估计配色后样品色度坐标的经验公式，结果显示白光样品色度坐标的实验值与经验公式估计值基本一致.     

CdSe/ZnSe/ZnS多壳层结构量子点的制备与表征

展示了一种简捷的多壳层量子点合成路线。在含有过量Se源的CdSe体系中直接注入Zn源,"一步法"合成了CdSe/ZnSe量子点;进一步以CdSe/ZnSe为"核",表面外延生长ZnS壳层制备了核/壳/壳结构CdSe/ZnSe/ZnS量子点。相对于以往报道的多壳层结构量子点的制备方法,该方法通过减少壳层的生长步骤有效地简化了实验操作,缩短了实验周期,同时减少对原料的损耗。对量子点进行高温退火处理,能够大幅提高CdSe/ZnSe/ZnS量子点的发光量子产率。透射电镜、XRD以及光谱研究表明:所制备的量子点接近球形,核与壳层纳米晶均为闪锌矿结构,最终获得的CdSe/ZnSe/ZnS量子点的光致发光量子产率达到53％。为了实现量子点的表面生物功能化,通过巯基酸进行了表面配体交换修饰,使量子点表面具有水溶性的羧基功能团,并且能够维持较高的光致发光量子产率。     

IR-active vibrational modes of CdTe and CdSe colloidal quantum dots and CdTe/CdSe core/shell nanoparticles and coupling effects

The frequencies of the vibrational modes of CdTe and CdSe quantum dots and CdTe/CdSe core/shell nanoparticles prepared by the colloid chemistry method are determined using IR transmission and IR reflection spectroscopy. The experimental IR transmission spectrum of CdTe and CdSe nanocrystals exhibits a broad minimum located between the frequencies of the transverse optical (TO) and longitudinal optical (LO) phonons of bulk CdTe and CdSe crystals. The frequencies of the modes for ensembles of CdTe and CdSe quantum dots are considerably shifted toward lower frequencies as compared to those calculated for single quantum dots. This is explained by the dipole-dipole interaction between quantum dots. The frequencies of modes for the structures with core/shell nanoparticles differ little from the calculated frequencies. This suggests a weakening of the interaction in these structures due to the enhancement of dielectric screening.