Formation and characterization of self-organized CdSe quantum dots

We have investigated the formation and characteristic of self-organized CdSe quantum dots (QDs) on ZnSe(001) surfaces with the use of photoluminescence (PL) and transmission electron microscopy (TEM). Coherent CdSe QDs are naturally formed on ZnSe surfaces, when the thickness of CdSe layers is around 2 ML. The plan-view TEM images exhibit that CdSe QDs have a relatively narrow distribution of QD size, and that the density of CdSe QDs is about 10¹⁰ cm⁻². The base structure of the CdSe dot is rhombic, which has the long axis of about 20 nm in length along direction. The temperature dependence of macro-PL spectra reveals that the behavior of self-organized CdSe QDs is quite different from that of ZnCdSe quantum well (QW), resulting from characteristic features of zero-dimensional structures of QDs. Moreover, the macro-PL results suggest the existence of QW-like continuous state lying over QD states. Micro-PL measurements show several numbers of high-resolved sharp lines from individual CdSe QDs. The linewidth broadening with temperature depends on peak energy position of the QDs. The linewidths of lower energy lines, corresponding to larger size QDs, are more temperature dependent.     

CdSe／PVK纳米晶薄膜及其电致发光特性

以巯基乙酸（RSH）为稳定剂，在水溶液中合成CdSe纳米晶，用表面活性剂将分散在水溶液中的纳米颗粒转移到有机溶剂中，与具有电荷输运性能的有机聚合材料复合。作为电致发光（EL）器件的工作层，得到较强的位于600nm附近的CdSe纳米晶的带边发射，以及较弱的位于420nm附近的来自聚合物的发射。器件EL强度首先随着外加电压的增加而增加，当电压超过26V时，EL强度开始下降。器件的电流-电压（I-V）特性基本符合二极管特性，表明器件是受载流子注入限制的。     

富镉CdSe单晶的气相生长及其电学特性

用改进的垂直气相法生长的富镉 Cd Se单晶 ,其电阻率为 10 7Ω· cm量级 ,电子陷阱浓度为 10 8cm- 3量级 ,且能将注入其中的部分电荷储存起来。分析认为 ,晶体的高电阻率及储存电荷的能力都是由 Se空位引起的 .     

Oxygen and indium diffusion into SiO2 encapsulated polycrystalline CdSe films

The diffusion of oxygen into SiO₂ encapsulated polycrystalline CdSe films and the diffusion of indium into polycrystalline CdSe films have been investigated over the temperature range 350 C to 500 C using SIMS. The oxygen profiles in the SiO₂ indicated that both isotopic oxygen exchange and the diffusion of molecular oxygen along short circuit paths were occurring with activation energies of 1.1 eV and 0.66 eV, respectively. The activation energies determined for the diffusion of the oxygen and indium in the grains (0.39 eV and 0.10 eV, respectively) were smaller than the values determined for the diffusion in the grain boundaries (0.70 eV and 0.78 eV, respectively), and was attributed to impurities and intrinsic defects accumulating at the grain boundaries.     

聚丙烯酰胺辅助溶剂热法合成CdSe纳米线

通过溶剂热法, 在180℃, 利用聚丙烯酰胺辅助合成了直径约为20nm, 长度为几百纳米到几微米的CdSe纳米线. 通过XRD、TEM、HRTEM表征了产物的结构和形貌, 并且讨论了反应时间对产物形貌的影响以及聚合物辅助纳米线生长的机制. 通过紫外-可见光谱和光致发光光谱研究了纳米线的光学性能, 在660nm处有一明显的吸收峰, 与体相材料相比具有明显的量子尺寸效应.     

Amplification of fluorescence emission of CdSe/ZnS QDs entrapped in a sol-gel matrix, a new approach for detection of trace level of PAHs

In this work, CdSe/ZnS core/shell QDs with emission wavelengths of 535 nm, 545 nm, 555 nm and 575 nm were synthesized and the ligands on their surface were exchanged with mercaptopropionic acid (MPA) to make them water-soluble. Hydrophilic QDs were incorporated into a sol-gel GA matrix of 3-aminopropyl trimethoxysilane (APTMS) and 3-glycidoxypropyl trimethoxysilane (GPTMS) to fabricate QD-entrapped membranes. The fluorescence intensity of the QDs entrapped in the sol-gel membrane was increased after being activated by the energy transfer from polycyclic aromatic hydrocarbon compounds (PAHs). The signal increase of the QDs was proportional to the increase in the concentration of the PAHs. Herein, trace levels of anthracene (ANT), phenanthrene (PHE) and pyrene (PYR) were detected through the enhancement of the fluorescence intensity of the CdSe/ZnS QD-entrapped membranes. The linear detection ranges were 0.01-0.1 μM for ANT and PHE and 0.005-0.05 μM for PYR. The QD-entrapped sol-gel membranes also showed quite good stability for the detection of PAHs over a period of 2 months.