Synthesis and Electrical Properties of a New Compound (BiSe)_0.97(Bi₂Se₃)_1.26(BiSe)_0.97(MoSe₂) Containing Metallic 1T-MoSe₂

The synthesis and electrical properties of a new misfit compound containing BiSe, Bi₂Se₃, and MoSe₂ constituent layers are reported. The reaction pathway involves competition between the formation of (BiSe)_1+x(Bi₂Se₃)_1+y(BiSe)_1+x(MoSe₂) and [(Bi₂Se₃)_1+y]₂(MoSe₂). Excess Bi and Se are required in the precursor to synthesize (BiSe)_1+x(Bi₂Se₃)_1+y(BiSe)_1+x(MoSe₂). High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) confirm the stacking sequence of the heterostructure. Small grains of both 2H- and 1T-MoSe₂ are observed in the MoSe₂ layers. X-ray photoelectron spectroscopy (XPS) indicates that there is a significantly higher percentage of 1T-MoSe₂ in (BiSe)_1+x(Bi₂Se₃)_1+y(BiSe)_1+x(MoSe₂) than in (BiSe)_0.97(MoSe₂), suggesting that more charge transfer to MoSe₂ occurs due to the additional BiSe layer. The additional charge transfer results in (BiSe)_1+x(Bi₂Se₃)_1+y(BiSe)_1+x(MoSe₂) having a low resistivity (14–19 μΩ m) with metallic temperature dependence. The heterogeneous mix of MoSe₂ polytypes observed in the XPS complicates the interpretation of the Hall data as two bands contribute to the electrical continuity.