Bi-Te薄膜材料的电化学制备及其热电性能研究

发布时间：2018-01-04 12:15

本文关键词：Bi-Te薄膜材料的电化学制备及其热电性能研究　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：对于合金热电薄膜材料,传统的制备方法如气相沉积、分子外延生长等存在着设备依赖性强、靶材价格昂贵和大面积制备困难等弊端。本论文采用电沉积的方法,通过调控电镀液成分及电沉积工艺参数,在金种层修饰的导电玻璃基底(Au/ITO)上,制备了较大面积的纯相n型Bi2Te3和p型BixTey热电薄膜材料,在具有良好的热电性能的同时降低成本、简化工艺。在10mM Bi3+15 mM HTeO2++1 M HNO3的电镀液体系中,实现了对不同表面形貌的纯相n型Bi2Te3热电薄膜的可控制备：当沉积电位为-0.20 V,沉积时间为120 s时制备的薄膜具有致密连续的麦粒状微观形貌,其电阻率为8.060×10-6Ω·m,载流子浓度为5.029×1020 cm-3,Seebeck系数为-64.949 μV·K-1,功率因子为5.234×104 W·m-1·K2,具有最佳的n型热电性能。在12.5 mM Bi3+12.5 mM HTe02++1M HN03的电镀液体系中,制备了具有Bi2Te3六方相结构的p型富Bi热电薄膜材料。在沉积电位为-0.25 V,沉积时间为60 s时制备的薄膜制具有致密连续的麦粒状微观形貌,其电阻率为4.525×10-6 Ω·m,载流子浓度为1.093×1021cm-3,Seebeck系数为57.168 μV.K-1,功率因子达了7.222×10-4W·m-1·K2,优于n型纯相Bi2Te3的热电性能,实现了自身掺杂对载流予类型的改变和性能的优化。对以上体系进行分析,研究Bi-Te薄膜的共沉积机理：Bi3+优先析出还原为Bi0,同时诱导HTeO2+发生欠电位沉积。在优选电位下,致密薄膜的形核过程为依附于金种层的均匀形核；其稳定生长阶段发生Bi3+、HTeO2+的共沉积反应,且此时受扩散步骤控制,晶核连续横向长大,相互连接形成致密薄膜。在此沉积机理的启发下,采用周期性脉冲双电位法,对Bi-Te纳米棒阵列的无模板辅助电沉积进行了探索。阵列薄膜中Bi-Te纳米棒的直径约为80～120nm,长度约为250nm,分散均匀。其生长过程可描述为：当体系加载短暂的还原电位时,工作电极上制备了均匀的岛状Bi-Te晶核,再加载氧化剥离电位时,溶解部分非晶态晶核中不稳定的Bi原子；如此反复多次,最终得到Bi-Te纳米棒阵列薄膜。
[Abstract]:For alloy thermoelectric thin film materials, the traditional preparation methods such as vapor deposition, molecular epitaxial growth have a strong equipment dependence. The price of target is expensive and the preparation of large area is difficult. In this paper, electrodeposition method is used to control the composition of electroplating solution and the parameters of electrodeposition process. A large area of pure n-type Bi2Te3 and p-type BixTey thermoelectric thin films were prepared on au / ITO substrate modified with gold seed layer. The electroplating bath system with 10mm Bi3 15mm HTeO2 1m HNO3 has good thermoelectric properties and lower cost and simplifies the process. The controllable preparation of n-type Bi2Te3 thermoelectric thin films with different surface morphologies was achieved: the deposition potential was -0.20 V. When the deposition time is 120 s, the films have dense and continuous wheat grain morphology, and their resistivity is 8.060 脳 10 ~ (-6) 惟路m. The carrier concentration is 5.029 脳 10 ~ (20) cm ~ (-3) ~ (-1) Seebeck coefficient is -64.949 渭 V 路K ~ (-1). The power factor is 5.234 脳 104 W 路m-1 路K2. It has the best n type thermoelectric properties in the electroplating bath system of 12. 5 mm Bi3 12. 5 mm HTe02 1 M HN03. Bi-rich p-type thermoelectric thin films with Bi2Te3 hexagonal phase structure were prepared at a deposition potential of -0.25 V. The thin films prepared at the deposition time of 60 s have dense and continuous micromorphology of wheat grains, and their resistivity is 4.525 脳 10 ~ (-6) 惟路m. The carrier concentration is 1.093 脳 1021cm-3. The Seebeck coefficient is 57.168 渭 V.K-1, and the power factor is 7.222 脳 10-4 W 路m-1 路K2. The thermoelectric properties of n-type pure phase Bi2Te3 are better than that of n-type pure phase Bi2Te3. The mechanism of co-deposition of Bi-Te thin films was studied. The precipitation and reduction of Bi-Te thin films were preferentially reduced to Bi0, and the underpotential deposition of HTeO2 was induced. The nucleation process of the dense film is uniform nucleation dependent on the gold seed layer. The codeposition reaction of Bi3 / HTeO2 occurs in the stable growth stage, which is controlled by the diffusion step, and the crystal nucleus grows laterally and connects with each other to form a compact film. The template-free assisted electrodeposition of Bi-Te nanorod arrays was investigated by means of periodic pulse double potential method. The diameter of Bi-Te nanorods in the array films was about 80 ~ 120nm. The growth process can be described as: when the system is loaded with a short reduction potential, a uniform island Bi-Te crystal nucleus is prepared on the working electrode. When the oxidation stripping potential is reloaded, the unstable Bi atoms in some amorphous nuclei are dissolved. Finally, Bi-Te nanorod array films were obtained after repeated times.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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