Structural influence on transport properties in [(PbSe)_1.00]_m(MoSe₂)_n misfit layered compounds

Abstract

The dependence of the electrical properties on the structural variation and annealing conditions are explored for the turbostratically disordered misfit layered compounds [(PbSe)1.00]m(MoSe2)n where m and n range between 1 and 5 layers. The thickness of the PbSe and MoSe2 layers both appear to have a significant impact on the transport properties of these materials, although variations in defect levels also make a significant contribution. When the thickness of the MoSe2 unit is thick relative to the PbSe unit, typically both a low resistivity (~0.05 Ωm) as well as a low Seebeck coefficient (~50 µV K−1) are observed, compared to when m and n are both small, which tends to result in a relatively high resistivity and moderate Seebeck coefficient. When the m is large (corresponding to a thick PbSe unit), a large, negative Seebeck coefficient (~−400 µV K−1) is observed simultaneous with a relatively low resistivity (0.01 Ωm). Considering the exceptionally low thermal conductivity values that have been reported for these compounds, this could be a promising regime for optimizing doping levels for thermoelectric applications, where a low electrical resistivity and high Seebeck coefficient result in high efficiencies.