Synthesis and Electronic Properties of the Misfit Layer Compound [(PbSe)1.00]1[MoSe2]1

An ultralow-thermal-conductivity compound with the ideal formula [(PbSe)(1.00)](1)[MoSe2](1) has been successfully crystallized across a range of compositions. The lattice parameters varied from 1.246 nm to 1.275 nm, and the quality of the observed 00a diffraction patterns varied through the composition region where the structure crystallized. Measured resistivity values ranged over an order of magnitude, from 0.03 Omega m to 0.65 Omega m, and Seebeck coefficients ranged from -181 mu V K-1 to 91 mu V K-1 in the samples after the initial annealing to form the basic structure. Annealing of samples under a controlled atmosphere of selenium resulted in low conductivities and large negative Seebeck coefficients, suggesting an n-doped semiconductor. Scanning transmission electron microscopy cross-sections confirmed the interleaving of bilayers of PbSe with Se-Mo-Se trilayers. High-angle annular dark-field images revealed an interesting volume defect, where PbSe grew through a region where a layer of MoSe2 would be expected in the perfect structure. Further studies are required to correlate the density of these defects with the observed electrical properties.