硒化锌纳米晶瞬态表面光伏与气敏特性研究

发布时间：2018-05-09 00:39

本文选题：第一性原理 + 吸附　；参考：《燕山大学》2015年硕士论文

【摘要】：ZnSe(110)表面与各种分子之间相互作用及催化氧化反应的研究对于提升ZnSe在气敏、催化等领域中的应用具有重要意义。本文采用密度泛函理论和周期性平板模型,分别计算了ZnSe(111)不同截止面和(110)表面的表面能,并结合实验结果所表明的量子点壳层主要生长面,着重研究O2、CO和CO2在ZnSe的非极性(110)表面的吸附行为和CO在ZnSe(110)表面的催化氧化过程。另外本文还制备了具有独特光电特性的以L-半胱氨酸(L-Cys)为配体修饰的ZnSe核壳结构量子点并研究了其光生载流子的输运行为。通过场诱导表面光电压技术和瞬态光电压技术结合表征了所制备ZnSe/ZnS/L-Cys核壳量子点的光伏特性。同时结合傅立叶变换红外光谱、拉曼光谱、紫外可见光吸收光谱和荧光光谱分析了样品的光电性能及载流子迁移行为。并使用VASP结合barder电荷对不同配体与ZnSe的相互作用和电荷转移进行了分析。计算结果表明:ZnSe不同截止面的(111)表面和(110)表面的表面能以(110)表面的表面能最低,最为稳定;O2、CO和CO2在ZnSe(110)表面均以化学吸附形式吸附,吸附能分别为0.455、0.296和0.326 eV。当O2优先于CO在表面吸附时更有利于CO催化氧化反应的发生。而且当表面存在Se空位时,O2分子以化学吸附形式优先吸附在ZnSe(110)表面的Se空位上并生成激发态O22。可以大大提高ZnSe(110)表面的氧化性,从而影响ZnSe(110)表面CO催化氧化反应。实验结果表明:ZnSe量子点具有P型光伏特性,并较同族核壳量子点在紫外-近红外区域具有更宽和更强的光电压响应。相位值随外加正电场绝对值的增加而增加,随外加负电场绝对值的减小而减小。在3.3×10-8到2×10-3 s区域宽的光电压响应与光生自由电荷载流子的扩散距离延长和界面空间电荷区明显的量子隧道效应有关,同时这也是导致所制备样品独特的光电压特性的原因。
[Abstract]:The study on the interaction between ZnSe110) and various molecules and the catalytic oxidation reaction is of great significance in enhancing the application of ZnSe in gas sensing, catalysis and other fields. In this paper, using density functional theory and periodic plate model, the surface energies of different cutoff surfaces and 110) surfaces are calculated, respectively, and the main growth surfaces of the shell layer of quantum dots are shown by the experimental results. The adsorption behavior of O _ 2CO and CO2 on the non-polar surface of ZnSe and the catalytic oxidation of CO on the surface of ZnSe _ (110) were studied. In addition, L- cysteine L-Cys-modified ZnSe core-shell quantum dots with unique optoelectronic properties have been prepared and their photoinduced carrier transport behavior has been studied. The photovoltaic properties of ZnSe/ZnS/L-Cys core-shell quantum dots were characterized by field-induced surface photovoltage technique and transient photovoltage technique. At the same time, the photoelectric properties and carrier migration behavior of the samples were analyzed by Fourier transform infrared spectroscopy, Raman spectroscopy, UV-Vis absorption spectrum and fluorescence spectrum. The interaction and charge transfer between different ligands and ZnSe were analyzed by VASP and barder charge. The calculated results show that the surface energy of the different cutoff surfaces of 1: ZnSe is the lowest, and the adsorption energy of CO and CO2 on ZnSe 110) surface is the lowest, and the adsorption energy is 0.455U 0.296 and 0.326 EV, respectively. When O _ 2 is preferentially adsorbed on the surface of CO, the catalytic oxidation of CO is more favorable. Moreover, when there is a se vacancy on the surface, O _ 2 molecules are chemically adsorbed preferentially on the se vacancy on the ZnSe110) surface and form an excited state O _ (22). The oxidation property of ZnSe110) surface can be greatly improved, thus affecting the catalytic oxidation of CO on ZnSe110) surface. The experimental results show that: ZnSe quantum dots have P-type photovoltaic properties and wider and stronger photovoltage response than the core-shell quantum dots in the UV-NIR region. The phase value increases with the increase of the absolute value of the applied positive electric field and decreases with the decrease of the absolute value of the applied negative electric field. The wide photovoltage response in the range of 3.3 脳 10-8 to 2 脳 10-3 s is related to the extension of the diffusion distance of photogenerated free charge carriers and the obvious quantum tunneling effect in the interfacial space charge region, which also contributes to the unique photovoltage characteristics of the prepared samples.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ132.41;TB383.1

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