Epitaxial MOCVD deposition of thermoelectric material films and determination of thermoelectric properties including thermal conductivity

热电材料薄膜的外延 MOCVD 沉积以及热电性能（包括热导率）的测定

• 批准号: 281725611
• 负责人: Professor Dr. Christian Jooss
• 金额: --
• 依托单位: Anorganische Chemie - AK Schulz
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/281725611?language=en
• 关键词: Epitaxial; MOCVD; deposition; thermoelectric; material

The goal of this project is the epitaxial MOCVD deposition of thin films of thermoelectric materials for technical application in the low (<350 °C) and medium (400 - 700 °C)) temperature range and the determination of their transport properties. Tailor-made metal organic group 15 and 16 precursors such as low-valent compounds E2R4 and E'2R'2 (E = Sb, Bi; E' = S, Se, Te) and single-source precursors R2EE'R', (R2E)2E', RE(E'R')2 und E(E'R')3 (E = Sb, Bi; E' = S, Se, Te), which cleanly decomposed at rather mild temperatures, will be investigated. Binary (Sb2Se3, Sb2Te3, Bi2Se3, Bi2Te3) and ternary material films (SbxBi1-x)2Te3, Sb2(SexTe3-x), Bi2(SexTe3-x) as well as complex multilayer structures will be epitaxially deposited in systematical MOCVD studies and a fundamental understanding of the influence of different chemical compositions on the thermoelectric properties, e.g. electrical and thermal conductivity and Seebeck coefficient will be developed. The characterization of the material films is essential in order to understand the specific influence of the precursor, deposition temperature, and substrate material on the thermoelectric properties of the resulting material films. The films will therefore be pre-characterized in the Schulz group (crystallinity, surface morphology, chemical composition). Promising films are then investigated in detail in the DFG- research infrastructure center ICAN (Interdisciplinary Center for Analytics on the Nanoscale, University of Duisburg-Essen; SAM, XPS, TOF-SIMS) and by our collaborators Dr. Gabi Schierning (Seebeck coefficient, power factor) and Prof. Axel Lorke (electrical conductivity). The determination of the thermal conductivity of the binary and ternary material films, which is crucial for the current project, will be done by Prof. C. Jooss using the 3-omega method. Careful investigation of the temperature-dependence of the thermal conductivity, which will be done in the temperature range from 30 K to 900 K, gives valuable information on the influence of phonon scattering at point disorder, grain boundaries (low temperatures) as well as phonon-phonon scattering (high temperatures). In addition, the defect and microstructure of selected samples will be investigated using high-resolution and analytical TEM. Non-stoichiometries at grain boundaries as well as point defects and defect clusters as function of synthesis parameters and doping levels are of particular interest and will be investigated using electron energy loss spectroscopy (EELS) and Annular Dark Field (ADF) techniques. In-situ TEM experiments will give information on behavior under thermal stress. The potential of superlattices on the further optimization of the thermoelectric properties of selected material systems will be studied. The in plane and cross plane coefficients of the thermal conductivity will be separated out for selected samples.

该项目的目标是热电材料薄膜的外延 MOCVD 沉积，用于低温（<350 °C）和中（400 - 700 °C）温度范围的技术应用，并确定其传输特性。制成金属有机基团 15 和 16 前体，例如低价化合物 E2R4 和 E'2R'2 (E = Sb, Bi; E' = S, Se, Te) 和单源前体R2EE'R', (R2E)2E', RE(E'R')2 和 E(E'R')3 (E = Sb, Bi; E' = S, Se, Te)，在相当高的温度下完全分解将研究二元（Sb2Se3、Sb2Te3、Bi2Se3、Bi2Te3）和三元材料薄膜（SbxBi1-x）2Te3， Sb2(SexTe3-x)、Bi2(SexTe3-x) 以及复杂的多层结构将在系统的 MOCVD 研究中外延沉积，并基本了解不同化学成分对热电性能的影响，例如电导率、导热率和塞贝克性能。为了了解前驱体、沉积温度和基底材料对所得材料薄膜热电性能的具体影响，材料薄膜的表征至关重要。因此，Schulz 小组将对其进行预先表征（结晶度、表面形态、化学成分），然后在 DFG 研究基础设施中心 ICAN（杜伊斯堡-埃森大学纳米尺度跨学科分析中心）进行详细研究。 SAM、XPS、TOF-SIMS）以及我们的合作者 Gabi Schierning 博士（塞贝克系数、功率因数）和 Axel Lorke 教授（电导率）。二元和三元材料薄膜的热导率对于当前项目至关重要，将由 C. Jooss 教授使用 3-omega 方法仔细研究热导率的温度依赖性。在 30 K 至 900 K 的温度范围内，提供了有关点无序、晶界（低温）以及声子-声子散射（高温）的声子散射影响的有价值的信息。所选样品的缺陷和微观结构将使用高分辨率和分析 TEM 进行研究，晶界以及点缺陷和缺陷合成簇作为参数和掺杂水平的函数特别令人感兴趣，并将使用电子能量进行研究。损耗光谱（EELS）和环形暗场（ADF）技术将提供有关热应力下超晶格行为的信息，从而进一步优化所选材料系统的热电性能。研究将针对选定的样品分离出面内和横截面的导热系数。