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1、目 录目 录摘 要IABSTRACTIII第一章绪 论11.1 研究意义11.2 钙钛矿氧化物中的光诱导效应51.2.1 光致金属-绝缘体相变51.2.2 光致的持续光电导效应71.2.3 光生载流子注入效应71.2.4 光生伏特效应91.3 本论文的主要研究内容意义11本章参考文献12第二章 钙钛矿氧化物异质结正向光电效应172.1 引言172.2 物理模型与方法182.3 LSMO/SNTO异质结制备与光伏效应测量介绍212.4 LSMO/SNTO异质结的正向光伏信号随时间演化过程以及相应的理论计算结果212.5 LSMO/SNTO异质结光电效应中的光掺杂效应以及其动态物理过程232.6
2、影响LSMO/SNTO异质结光电响应的几个因素272.7 小结31本章参考文献32第三章 钙钛矿氧化物异质结的侧向光电效应353.1 绪论353.2 描述稳态侧向光电效应的Lucovsky模型简介以及对其局限性的讨论363.3 描述侧向光电效应的二维含时漂移-扩散模型413.4 含时二维漂移-扩散模型的求解困难以及解决方案423.5 正常的侧向光电效应和在钙钛矿氧化物异质结中发现的反常侧向光电效应443.6 Dember效应463.7 钙钛矿氧化物异质结中反常侧向光电效应的理论解释和相应的数值计算结果473.8 小结52本章参考文献53总结和展望55攻读博士学位期间完成的学术论文目录57A第一
3、作者学术论文57B非第一作者学术论文57C会议58致 谢59i摘 要钙钛矿氧化物异质结光电效应的理论研究摘 要在本论文中，我们以漂移-扩散模型为基础发展出了一套描述钙钛矿氧化物异质结光电效应的物理模型，然后对此模型进行了自洽计算，通过计算对钙钛矿氧化物异质结光电效应中出现的物理问题进行了分析和解释。本文的主要工作和取得的结论如下：1 在漂移-扩散模型和界面Richardson热电子发射模型的基础上建立起了描述钙钛矿氧化物异质结光电效应的动态物理过程的物理模型。并对此模型进行了自洽计算。理论计算所得到的结果同我们试验结果有着很好的符合，这说明我们建立的物理模型是适于描述钙钛矿氧化物异质结光电效应
4、的。2 在Sr-doped LaMnO3/Nb-doped SrTiO3异质结的正向光电效应的理论计算中，我们特别分析其中载流子浓度分布随时间的演化过程，发现在光电效应的过程中载流子浓度的变化主要是集中在异质结的空间电荷区附近，而在空间电荷区外，载流子浓度相对变化非常小，这说明在钙钛矿氧化物异质结中光掺杂效应主要是集中在空间电荷区内，进而说明光对钙钛矿氧化物异质结材料的性质的调控也是主要集中在其中的空间电荷区内的。3 通过理论计算，我们发现光伏效应的测量电路中并联的电阻越小光电响应的速度就会越快，但是响应的灵敏度同时又会降低。我们还分析光子能量对光电相应的影响，发现光子能量越高，所导致的光电响
5、应速度越快而且灵敏度越高。4 分析了传统描述侧向光电效应的Lucovsky模型的缺陷，解释了为什么这套模型不能描述脉冲强激光条件下产生的侧向光电效应。进而我们又以二维含时漂移-扩散模型为基础，建立起了一套描述钙钛矿氧化物异质结侧向光电效应的动态物理模型，这套模型不但可以描述传统的稳态侧向光电效应同时也能描述动态侧向光电效应。5 使用二维含时漂移-扩散模型，分析了在La0.9Sr0.1MnO3/Sr0.99Nb0.01TiO3，La0.7Sr0.3MnO3/Si异质结中发现的一种反常侧向光电效应。并从计算上证实这种反常效应是由强脉冲激光所造成的强的Dember效应产生的。同时我从计算上得到侧向光
6、电效应随着激光强度增强从正常的侧向光电效应向反常侧向光电效应转变的过程的，进一步证明了我们对钙钛矿氧化物异质结反常侧向光电效应的解释。关键词： 钙钛矿氧化物，异质结，光电效应Theoretical studies on the photoelectric properties of perovskite oxide heterojunctionsABSTRACTIn this work, based on the drift-diffusion model, a theoretical model is developed for describing photoelectric effect
7、 in perovskite oxide heterojunctions. We solved the equations in this model with the self-consistent calculation. By the calculated results, some phenomena of photoelectric effect in this system are analyzed and explained. The obtained results are listed as follows:1. We develop a theoretical model
8、to describe the dynamic photoelectric effect in the pervoskite oxide heterojunction by drift-diffusion model and the Richardson thermal emission current on the interface and apply self-consistent calculation on these formulas. The obtained theoretical results agree well with the experimental results
9、, which indicate the validness of this model applying on the perovskite oxide heterojunction.2. The evolution of carriers concentration in Sr-doped LaMnO3/Nb-doped SrTiO3 heterojunction is analyzed by this model, and it is found that the carriers variation mainly locates in the space-charge region o
10、f heterojunction and there is no pronounced variation in the other region. In other word, the photodoping effect in photoelectric process of perovskite oxide heterojunction is located in the space-charge region, or for a perovskite oxide heterojunction, the modulation of material properties by light
11、 is feasible merely in the space-charge region.3. By theoretical calculation, it is found that, for a perovskite oxide heterojunction, the less is the parallel resistance in the circuit for photovoltage measurement, the faster is the photovoltaic response and the lower is the sensitivity of photovol
12、taic response. The more powerful energy of photon is irradiated on the heterojunction, the faster and higher is the photovoltaic response. 4. We analyze the limitation in the classical theoretical model (Lucovsky model) for the lateral photovoltaic effect in pn junction and give an explanation why t
13、his classic model cannot describe the lateral photovoltaic effect with a pulse laser. Furthermore, based on the 2-dimensional time-dependent drift-diffusion model, we develop a general lateral photovoltaic model, which can describe not only the stable lateral photovoltaic effect but also the dynamic
14、 photovoltaic effect with pulse laser.5. By applying this model, we analyze the novel lateral photovoltaic effect，which is experimentally found in the La0.9Sr0.1MnO3/Sr0.99Nb0.01TiO3，La0.7Sr0.3MnO3/Si heterojunctions. We theoretically prove the explanation that this novel lateral photovoltaic effect
15、 is induced by the enhancement of Dember effect in the heterojunction with a strong pulse laser. At same time, it is obtained that the process of the lateral photovoltaic effect evolving from the normal one to the novel one, which give a further confirmation for the explanation that the novel lateral photovoltaic effect is induced by the strong irradiation. Keywords：Perovskite Oxide, Heterojunction, Photoelectric effect III第一章 绪 论第一章 绪 论1.1研究意义图1.1，氧化物材料的特异性质和若干应用领域硅半导体的发现以及随后半导体电子学的飞速发展，极大地
