铁电纳米管阵列的量子尺寸效应及光电耦合机制研究

Lead-free bismuth-based ferroelectric materials (bismuth ferrite, bismuth aluminate, bismuth titanate, etc.) have the advantages of low cost, low leakage current, good photovoltaic properties, and environmental friendliness. Therefore, these materials are expected to used in the fields of photovoltaic solar cells, infrared detectores, nonvolatile memories, microdrives and others. At present, many investigations about the films of preparation, physical properties, and applications has been reported. Howe, the design, preparation, characterizations and applications of the ferroelectric nano-structure are in the primary stage, which should be further investigated. In this project, the optical, electrical, and magnetic properties of element doping bismuth ferrite, bismuth aluminate, and bismuth titanate thin films and nanotube arrays will be investigated. Firstly, the temperature dependences of dielectric and ferroelectric properties of lanthanum and manganese co-doped bismuth ferrite thin films will be studied to clarify the leakage current mechanism, and then new concepts and techniques are proposed to control the leakage phenomenon. Based on the investigation, we will prepare high quality bismuth bismuth ferrite, bismuth aluminate, bismuth titanate arrays and investigate the relationships between optical, electrical and other physical behaviors and quantum size effects at various temperatures, electric and magnetic fields. Finally, the low dimension Bi-based ferroelectric materials will be effect explored in the field of photovoltaic solar cell, infrared detectors, and information storage.

无铅铋基铁电材料（铁酸铋、铝酸铋和钛酸铋等）具有成本低、漏电小、光电压大和环境友好等优点，有望在光伏太阳能电池、红外探测、非易失性存储器、微驱动器等领域得到广泛的应用。目前相关研究处于铁电薄膜结构的制备、性质和应用阶段。然而，铁电纳米结构的设计、制备、性质和应用有待进一步的研究和发展。本课题以元素掺杂铁酸铋、铝酸铋和钛酸铋薄膜和纳米管阵列作为研究对象，首先通过对镧锰元素的掺杂铁酸铋薄膜进行变温介电、铁电等电学研究，澄清铁酸铋材料的漏电机制，相应地提出有效克服漏电现象的新概念和新技术。在此基础上制备高质量铁酸铋、铝酸铋和钛酸铋等铁电纳米管阵列，在不同的温度、电场和磁场下研究其光电耦合特性及其量子尺寸效应。最后，对低维结构铋基铁电材料在光伏太阳能电池、红外探测和信息存储等领域的应用进行有效的探索。

无铅铋基铁电材料具有成本低、漏电小、光电压大和环境友好等优点，有望在光伏太阳能电池、红外探测、非易失性存储器、微驱动器等领域得到广泛的应用。本项目以铁酸铋、铌钛酸铋等低维铁电材料为对象系统深入地研究了其光电响应以及铁电特性。以铌钛酸铋为例，我们制备了高质量不同Mn掺杂铌钛酸铋薄膜并优化了Mn元素掺杂浓度。由变温拉曼和变温椭圆偏振光谱得到的光学声子模式和带间电子跃迁能量用来分析该体系的相变过程。通过分析变温（0-450℃）拉曼和椭圆偏振光谱得到光学性质和相变规律，研究表明该体系随着温度的升高经历了R3C-中间相-P4/mbm等一系列相变过程，光谱光学手段为探索铁电材料的相变规律提供了新的视角。另外，该体系的晶体结构、表面样貌、晶格振动、光学常数及带隙都做了详细的讨论。最后深入探讨了铁电响应、储能特性和漏电流相关的物理机制以及介电、损耗特性。根据P-E曲线，我们得到了1400 kV/cm下的最大可获得能量存储密度(19.84 J/cm3)，表明Mn掺杂能有效提高BNT薄膜电容器的储能能力和绝缘性。更近一步，我们把合成的纳米管成功转移到带有标记的硅/二氧化硅衬底上，采用电子束光刻技术实现了铁电纳米管元器件的制备，以此研究单根铁电纳米管在深低温、高温高压、强磁场/电场等极端环境下量子尺寸效应、光电耦合特性和铁电/压电响应。该项目关于无铅铁电材料低维结构的研究为其在光电、信息存储领域的应用提供了理论依据和实验基础。