过渡金属氧化物异质结光伏效应研究

发布时间：2018-04-17 00:00

本文选题：光伏效应 + 超导相关异质结　；参考：《中国科学技术大学》2017年博士论文

【摘要】：与传统的半导体异质结相比,过渡金属氧化物异质结有着非常丰富的物理性能,尤其在强关联体系中,其特殊的物理性质,如:超导电性、铁电性等,对异质结的电输运性质有着显著地调控作用,并可以实现一些非常有应用价值的功能。不仅如此,这些强关联材料及其异质结对光辐照也有着非常奇特的效应。这些效应对于研究光电薄膜器件有着拓展性的意义,尤其对于功能性的光电器件有着很多的应用价值。在本论文中,我们对高温超导材料及其异质结、铁电异质结等光、电相关的效应进行了系统研究。整个论文包含六章,内容概括如下:第一章从异质结的基本性质和光电相关的特性出发,介绍了在半导体Nb-掺杂的SrTiO3上构建的超导、铁电以及金属异质结及其界面状态、光电过程的原理与特征的物理现象,并探讨了最新的研究相关研究进展。第二章中设计了一种测量金属或半导体等材料的电磁及光电性能的多功能样品杆,尤其是使材料受电场、磁场,特别是光场的同时作用,测量固体材料在外场作用下的介电、铁电以及光电输运等物理性质及其变化。第三章中,系统的研究了 YBa2Cu307-δ/Nb-dopedSrTi03异质结在不同波长下的光伏效应,当光子能量为2.4eV时(远低于Nb-dopedSrTi03的能隙)也会有一定的光生电压大小。并通过I-V特性随温度的变化,发现光生电压和光生电流随温度的变化在120K附件有明显跳变行为,这与SNTO单晶衬底在低温下结构相变有密切关系。第四章中,研究了 Pt/BiFe03(BFO)/SNTO异质结(BFO厚度分别为60 nm和200 nm)在不同波长激光照射下的光伏效应和二极管整流行为。并且两种波长照射下的短路电流表现出了两个量级大小的差别,表明其有着不同的光激发机制。随着光强的增加,光辅助的二极管特性的整流比逐渐变大,但是开启电压保持不变。第五章中,Au(Pt)/SNTO肖特基结在不同波长的激光辐照下,都观察到了明显的光伏响应,且光伏的结果与入射的光子能量存在着密切的关系。通过研究该类肖特基结的光生电压与光生电流随光子能量的变化,发现该异质结表现出较好的符合肖特基结的特性,尤其对于Au/0.7wt%Nb-dopedSTO样品,还通过I-V特性的肖特基拟合,以及室温下的C-V特性,分别拟合得到了温室下肖特基势垒的大小并比较。此外变温的光伏测试表明,其光生电压的变化明显的受到电子热激发作用调制。第六章,研究了在不同温度、不同磁场大小和角度下BaFe1.8Co0.2As2单晶的I-V特性,并根据涡旋玻璃理论进行了标度,其结果满足3D涡旋玻璃转变理论。并且角度依赖的涡旋玻璃转变场Hg和临界电流密度Jc可以较好地满足各向异性的Ginzburg-Landau模型。我们还构建了 BaFe1.8Co0.2As2单晶的三维磁通相图,得到了磁通玻璃态、磁通液态,以及正常态随磁场角度的变化。
[Abstract]:Compared with the traditional semiconductor heterojunction, the transition metal oxide heterostructure has very rich physical properties, especially in the strongly correlated system, its special physical properties, such as superconductivity, ferroelectricity, etc.It can regulate the electrical transport properties of heterojunction and realize some very valuable functions.Not only that, these strongly related materials and their heterogeneity also have very peculiar effects on light irradiation.These effects are of great significance for the study of optoelectronic thin film devices, especially for functional optoelectronic devices.In this thesis, the optical and electrical effects of high temperature superconducting materials and their heterostructures, ferroelectric heterostructures are systematically studied.The whole thesis consists of six chapters, which are summarized as follows: in the first chapter, the superconducting, ferroelectric and metal heterojunctions and their interface states are introduced based on the basic properties of heterojunction and optoelectronic properties.The principle and characteristic physical phenomena of optoelectronic process are discussed.In the second chapter, a multifunctional sample rod is designed to measure the electromagnetic and optoelectronic properties of metals or semiconductors, especially to measure the dielectric properties of solid materials under the action of electric field, magnetic field, especially light field at the same time.Physical properties and changes of ferroelectricity and photoelectric transport.In chapter 3, the photovoltaic effect of YBA _ 2Cu _ 307- 未 / Nb-doped SrTi03 heterojunction at different wavelengths is systematically studied. When the photon energy is 2.4eV (far lower than the energy gap of Nb-dopedSrTi03), there is also a certain photogenerated voltage in YBA _ 2Cu _ 307- 未 / Nb-dopedSrTi03 heterojunction.Through the change of I-V characteristics with temperature, it is found that the variation of photovoltage and current with temperature has obvious jump behavior at 120K accessory, which is closely related to the structural phase transition of SNTO single crystal substrate at low temperature.In chapter 4, the photovoltaic effect and diode rectifying behavior of Pt/BiFe03(BFO)/SNTO heterojunction with thickness of 60 nm and 200 nm respectively under different wavelengths of laser irradiation are studied.The short circuit current of the two wavelengths is different in order of magnitude, which indicates that the short-circuit current has different photoexcitation mechanism.With the increase of light intensity, the rectifying ratio of photo-assisted diodes becomes larger, but the switching voltage remains the same.In chapter 5, the photovoltaic response of Au-PtN / SNTO Schottky junction is observed under different wavelengths of laser irradiation, and the photovoltaic results are closely related to the incident photon energy.By studying the variation of photogenerated voltage and photogenerated current with photon energy, it is found that the heterojunction exhibits good Schottky junction characteristics, especially for Au/0.7wt%Nb-dopedSTO samples, and is fitted by Schottky fitting of I-V characteristic.The size of Schottky barrier in greenhouse was fitted and compared with the C-V characteristic at room temperature.In addition, the photovoltaic measurements show that the change of photovoltage is obviously modulated by the electron-thermal excitation.In chapter 6, the I-V characteristics of BaFe1.8Co0.2As2 single crystals at different temperatures and different magnetic field sizes and angles are studied, and the results are calibrated according to the theory of vortex glass. The results satisfy the 3D vortex glass transition theory.The angle-dependent vortex glass transition field Hg and critical current density J _ c can well satisfy the anisotropic Ginzburg-Landau model.The three-dimensional flux phase diagram of BaFe1.8Co0.2As2 single crystal is also constructed. The flux glass state, flux liquid state and normal state vary with the angle of magnetic field.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O484.4;O611.62

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