Synthesis, characterization, and electronic structure of few-layer MoSe₂ granular films

Abstract

Few-layer MoSe2 granular films were prepared using rapid thermal processing (RTP) of stacked elemental layers (SELs) deposited using electron beam evaporation in the sequence of Mo/Se/Mo. RTP was carried out at various temperatures ranging from 550 to 750 °C, and durations ranging from 90 to 150 s. Morphology and microstructure of granular thin films were characterized by atomic force microscopy and scanning electron microscopy. Compositional and electronic structure analysis of the films were done by X-ray photoelectron, photoluminescence and Raman spectroscopy. The results confirmed the formation of four-layer MoSe2 granular thin films at 750 °C for 90 s. Density functional theory calculations showed that the direct gap at K is near degenerate with the calculated indirect band gap in the 4L structure. In addition to RTP, Raman laser annealing (RLA) was performed on SELs with various laser powers. Raman spectroscopy results reveal the local formation of MoSe2 with increasing laser energy.