Department of Chemistry, University of Oregon , Eugene, Oregon 97403-1253, United States.
Department of Physics and Astronomy University of Toledo , Toledo, Ohio 43606-3390, United States.
Nano Lett. 2017 Mar 8;17(3):1978-1986. doi: 10.1021/acs.nanolett.6b05402. Epub 2017 Feb 13.
We report cross-plane thermoelectric measurements of misfit layered compounds (SnSe)(TiSe) (n = 1,3,4,5), approximately 50 nm thick. Metal resistance thermometers are fabricated on the top and bottom of the (SnSe)(TiSe) material to measure the temperature difference and heat transport through the material directly. By varying the number of layers in a supercell, n, we vary the interface density while maintaining a constant global stoichiometry. The Seebeck coefficient measured across the (SnSe)(TiSe) samples was found to depend strongly on the number of layers in the supercell (n). When n decreases from 5 to 1, the cross-plane Seebeck coefficient decreases from -31 to -2.5 μV/K, while the cross-plane effective thermal conductivity decreases by a factor of 2, due to increased interfacial phonon scattering. The cross-plane Seebeck coefficients of the (SnSe)(TiSe) are very different from the in-plane Seebeck coefficients, which are higher in magnitude and less sensitive to the number of layers in a supercell, n. We believe this difference is due to the different carrier types in the n-SnSe and p-TiSe layers and the effect of tunneling on the cross-plane transport.
我们报告了错层层状化合物 (SnSe)(TiSe)（n = 1,3,4,5）的平面热电器件测量结果，其厚度约为 50nm。在 (SnSe)(TiSe) 材料的顶部和底部制造金属电阻温度计，以直接测量材料的温度差和热传输。通过改变超晶格中的层数 n，我们在保持全局化学计量比不变的情况下改变界面密度。跨 (SnSe)(TiSe) 样品测量的塞贝克系数强烈依赖于超晶格中的层数 (n)。当 n 从 5 减少到 1 时，平面热电器件的平面塞贝克系数从 -31 减少到 -2.5 μV/K，而由于界面声子散射的增加，平面有效热导率降低了两倍。(SnSe)(TiSe) 的平面热电器件的塞贝克系数与平面塞贝克系数非常不同，后者的幅度更高，对超晶格中的层数 n 不太敏感。我们认为这种差异是由于 n-SnSe 和 p-TiSe 层中的载流子类型不同以及隧道效应对平面热输运的影响所致。
