低维Bi2Te3材料热电性能太赫兹光谱研究

Microscopic physical mechanism for the thermoelectric properties of low-dimensional thermoelectric materials, such as Bi2Te3, has attracted intensive attention. In this proposal, the ultra-broadband terahertz time-domain spectroscopy in the range of 0.1-20THz will be used to effectively measure and analyze the transportation of carrier and phonon, which determine the macroscopic thermoelectric properties of the materials.Firstly,The spectral response of thermoelectric materials will be studied and the optical parameters like the conductivity will be extracted. The transferring phenomenon of the carrier and phonon will be described and analyzed effectively in effective medium theory and Drude-Smith model. Then, the dynamics process of the thermoelectric properties affected by the carrier concentration and temperature will be explored. In addition, the mechanism affecting the quality of thermoelectric conversion, such as the transportation of carriers and phonon, interface scattering effect and quantum size effect, will be investigated. The terahertz time-domain spectroscopy with the property of coherent measuring can draw out the eigenvalue of complex refractive index and complex electric conductivity directly, and avoid the contacting potential of electrodes. Therefore, the results can provide a new approach to measure and analyze the conductive properties for the low-dimensional thermoelectric materials, and explore a new access to develop thermoelectric microdevices.

针对影响低维热电材料性能的微观物理机理问题，以低维Bi2Te3材料为研究对象，采用相干宽谱(0.1-20THz)太赫兹时域光谱技术，有效测量并分析载流子和声子的传输特性对材料宏观热电性能的影响。拟研究该类热电材料在太赫兹波段的宽频、超快光谱响应，获得材料复电导率等数据；基于有效介质理论和Drude-Smith模型，有效提取与分析载流子和声子传输参数；在此基础上研究载流子浓度和温度影响材料热电性能的动力学过程，探索载流子与声子的传输、界面散射效应和量子尺寸效应等因素影响热电转换性质的作用规律。太赫兹时域光谱技术具有相干测量特性，避免了外加电极测量中接触电势的影响，能够直接获取材料复折射率和复电导率的本证值，将提供一套有效检测分析低维热电材料导电性能的新方法和手段，为发展热电微型器件开辟一条新途径。

项目获得多种物质的太赫兹光谱响应，提取折射率、吸收系数、电导率等参数，完善了针对不同类型样品的参数提取方法，解决了数据处理中的相位跳变问题。实现了宽频太赫兹光谱的高精度测量。基于气体等离子体产生和探测的超宽带太赫兹时域光谱系统可以实现宽带太赫兹光谱测量，通过提高扫描精度、直线度、增长扫描窗口等措施有效提高信噪比和光谱分辨率。建立了低维材料数据处理模型。形成了较完善的太赫兹光谱测量和分析手段，为有效提取低维材料的本征参数奠定了方法基础。