【作者】 王涛；

【导师】 靳正国；

【作者基本信息】 天津大学 ， 材料学， 2010， 硕士

【摘要】 金属硫族化合物是一类重要的半导体材料,由于其独特的物理和化学性能,在许多领域都具有广泛的应用前景。特别是近十几年对其结构、维度和形貌的调控,已进一步开拓了其光、电和磁等性能的新应用。本文以硝酸镉和亚硒酸钠作为镉源和硒源,氨水、EDTA为络合剂,水合肼为还原剂,在水溶液中通过低温回流反应研究了CdSe晶体的合成,采用XRD、EDS、XPS、TEM、SEM、HRTEM和UV-vis等手段对所得样品进行了测试表征。论文考察了不同络合剂、回流反应时间、Cd2+离子浓度、Cd/Se离子配比以及PEG4000、柠檬酸钠和巯基乙酸等辅助添加剂对产物晶型和形貌的影响,从化学反应原理及动力学角度探讨了过程机理。结果表明,选用EDTA和氨水作络合剂分别得到了较为纯净的闪锌矿相和纤锌矿相CdSe,体系回流2小时已基本反应完全,Cd和Se化学计量比分别约为1:1和3:2。Cd2+离子浓度过高或过低都会发生副反应而引入CdSeO3、Se等杂质。Cd/Se的比值会影响产物粒径和形貌,产物的粒径在一定范围内随Cd/Se比值的增加而增大,Cd/Se比过高会形成一种分枝结构。XPS测试分析表明在没有添加剂的情况下,水溶液法制备的CdSe表面被Cd(OH)2等杂质包覆。通过样品的UV-vis漫反射光谱,估算出EDTA和氨水体系所得样品的禁带宽度Eg分别为1.63eV和1.70eV。由于产物粒径大于玻尔半径,闪锌矿和纤锌矿相的CdSe都没有表现出明显的量子限域效应。更多还原

【Abstract】 Metal chalcogenide as an important kind of semiconductor materials have a wide application prospect in many fields due to their unique physical, chemical properties. In particular, the optical, electrical and magnetic properties have been developed by altering their structure, dimension or morphology in recent ten years. In this paper, CdSe crystals were prepared through aqueous solutions using cadmium nitrate and sodium selenite as precursors, ammonia and EDTA as complexing agents, N2H4?H2O as a reducing agent. XRD, EDS, XPS, TEM, SEM, HRTEM and UV-vis were utilized to characterize chemical composition, crystal structures, morphology and optical properties of the CdSe crystals.Effects of processing parameters including complexing agents, refluxing time, concentration of Cd2+, the Cd/Se ratios and the stabilizers such as PEG4000, sodium citrate and thioglycolic acid were mainly investigated. The chalating action of EDTA and ammonia in dynamics of synthetical reaction was also discussed. Experimental results showed that the zinc blende and wurtzite CdSe crystals were obtained in the solution systems respectively containing EDTA and ammonia as complexing agents. When Cd2+ concentration of the solution with ammonia chalating was higher than 0.15mol/L and lower than 0.05mol/L, less CdSeO3 and Se beside CdSe main phase were found respectively. The ratio of Cd/Se played an important role in controlling the size and morphology of CdSe. The crystal sizes increased with the Cd/Se ratio in the range from 1 to 3. A branch crystal was formed as the Cd/Se ratio was more than 4. The stoichiometrical ratio of cadmium and selenium for the zinc blende and wurtzite CdSe crystals were 1:1 and 3:2 respectively according to EDS analysis. XPS spectra showed that Cd(OH)2 and SeOx(x≤1) compounds were easy to be formed on the surface of CdSe crystals from solution without stabilizers. Calculated from the UV-vis reflection spectra, the optical band gap of the zinc blende and wurtzite CdSe crystal was 1.63eV and 1.70eV respectively, no indicating the quantum confinement effect due to larger sizes of CdSe than the diameter of Bohr exciton in CdSe.更多还原