Cross-Plane Seebeck Coefficient Measurement of Misfit Layered Compounds (SnSe)<sub>n</sub>(TiSe<sub>2</sub>)<sub>n</sub> (n = 1,3,4,5).
basic_science · Level V
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- Record sourced from PubMed, PMID 28177640.
- Also identified by DOI 10.1021/acs.nanolett.6b05402.
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Abstract
We report cross-plane thermoelectric measurements of misfit layered compounds (SnSe)<sub>n</sub>(TiSe<sub>2</sub>)<sub>n</sub> (n = 1,3,4,5), approximately 50 nm thick. Metal resistance thermometers are fabricated on the top and bottom of the (SnSe)<sub>n</sub>(TiSe<sub>2</sub>)<sub>n</sub> 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)<sub>n</sub>(TiSe<sub>2</sub>)<sub>n</sub> 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)<sub>n</sub>(TiSe<sub>2</sub>)<sub>n</sub> 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<sub>2</sub> layers and the effect of tunneling on the cross-plane transport.