【作者】 侯杰；

【导师】 杨君友；

【作者基本信息】 华中科技大学 ， 材料学， 2006， 硕士

【摘要】 热电材料是一种利用固体内部载流子运动实现热能和电能直接相互转换的功能材料。它可用于温控、温差发电、医疗器材、潜艇用空调设备等许多重要领域。传统热电材料普遍ZT值较小,转换效率低。研究表明,材料的纳米化、低维化都有助于降低材料的热导率,是提高热电材料性能的最有效途径之一。电化学原子层外延法(ECALE)具有低成本、过程易控、室温沉积、环境负荷小等特点,在制备纳米超晶格材料方面具有独特的优势,是控制半导体化合物结构、组成和生长形貌及了解电沉积机理的先进技术。本文讨论了利用ECALE技术制备铋化碲纳米薄膜的研究过程,进而研究了碲在多晶金衬底上的沉积动力学特征。本文阐述了材料的热电效应机理,综述了热电材料的研究现状;对比常用制备薄膜材料的方法,详细介绍了电化学原子层外延技术的原理、特点和影响因素,并对电化学原子层外延技术在新材料中应用进行了展望。采用电化学原子层外延法(ECALE)在Au电极上成功地制备了Bi2Te3化合物热电薄膜。通过循环伏安扫描研究Te和Bi在Au衬底上的电化学特性,使用自动沉积系统交替欠电位沉积Te,Bi原子层200个循环获得沉积物。XRD,EDX和FESEM测试结果表明循环沉积200层后得到的沉积物Bi和Te的化学计量比为2:3,且是Bi2Te3薄膜化合物,而非单质Bi和Te的简单混合;薄膜均匀、致密、平整且可重复性好,以(015)为最优取向外延生长的。利用循环伏安(CV)技术对Te在多晶Au上和在沉积了一层Bi的多晶Au上的欠电位沉积的电化学特性进行了比较,并研究了PH值、浓度、扫描速率对Te欠电位的影响,同时验证了Te的欠电位沉积过程符合M.S. Maestre导出的三个标准,即遵循二维生长机制。更多还原

【Abstract】 Thermoelectric material is new functional material that can be used to convert thermal energy into electrical energy directly with carriers. It has been used in many fields, such as temperature control, thermoelectric power, cooling electronic devices, medical equipment, high temperature superconductor, aerospace equipment, air-conditioning of submarine and so on. The study shows that nano-crystallization or low dimensionization is one of the most effective methods to improve thermoelectric.Electrochemical atomic layer epitaxy(ECALE) exhibites outstanding properties, such as low cost, easily controllable and scalable process, deposition at ambient temperature and environmental benign and so on. ECALE is proved to be an advanced method for deposition of semiconductor compound nanofilms.The preparation of Bi2Te3 thin film by ECALE and kinetics of Te on Au and Bi-Au were discussed in this paper. Firstly, we introduced the research background of this work and made a detailed review to the basic principles, characteristic and influence factors and application of ECALE method, and the perspective and application of ECALE in new material is estimated.The process of Bi2Te3 thin film growth on Au substrate by using electrochemical atomic layer epitaxy (ECALE) was reported in this thesis. Cyclic voltammetic method was used to investigate the electrochemical aspects of Bi and Te on the Au substrate. On the basis of analysis, we found the peak of 0.1~0.3V is the UPD peak of Te on Au, and the peak between 0~-0.3V is the UPD peak of Te on Bi covered Au. The ECALE program was optimized and a 200-cycle film was deposited. X-ray diffraction, EDX quantitative analysis and FESEM observation were performed to characterize the substrates and deposits, and the results shows that the deposits are single phase Bi2Te3 compound with a 2:3 stoichiometric ratio of Bi to Te; and the deposits are dense and homogeneous with a (015) preferred orientation.Electrochemical kinetic behavior of Te on Au and on Bi-Au has been studied using voltammetry and chronoamperometry techniques, effects of PH value, concentration and scan rate were reported. Scan rate dependent cyclic voltammetry experiments reveals that the UPD process of the Bi layer from an Au electrode fulfilled three criteria. That means 2-D growth mechanism is the dominant process in the UPD process of Te.更多还原