Synthesis and characterization of Mo and W compounds for disulfide materials

Abstract

MoS₂ and WS₂ are spotlighted as fungible materials of graphene that can be used in electronic devices owing to being semiconductors with indirect and direct band gaps. Precursors (Mo(N^tBu)₂(S^tBu)₂ (1), W(N^tBu)₂(S^tBu)₂ (2)) suitable for the deposition of these materials were synthesized and characterized. The molecular structures of 1 and 2 exhibit a tetrahedral geometry according to single-crystal x-ray crystallography. Thermogravimetric analyses of 1 and 2 showed two-step weight loss. The residues from each step of 1 were MoS₃ and MoS₂, and these results were consistent with the subsequent deposition results of 1. We successfully established a PEALD-MoS₂ process using 1 and H₂S plasma as the precursor and reactant, respectively, at relatively low temperatures of 150–300 °C without any post-sulfurization process. A temperature-dependent selective deposition of MoS_x phases was observed with the growth of amorphous MoS₃ films (150–200 °C), and crystalline MoS₂ films (250–350 °C).