Chemically exfoliated MoS2 layers: Spectroscopic evidence for the semiconducting nature of the dominant trigonal metastable phase

A metastable trigonal phase, existing only as small patches on a chemically exfoliated few-layered, thermodynamically stable H-1 phase of MoS2, is believed to critically influence the properties of MoS2-based devices. The electronic structure of this metastable phase is little understood in the absence of a direct experimental investigation of its electronic properties, complicated further by conflicting claims from theoretical investigations. We address this issue by investigating the electronic structure of this minority phase in chemically exfoliated MoS2 few-layered systems by enhancing its contributions with the use of highly spatially resolved (<= 120 nm resolution) photoemission spectroscopy and Raman spectroscopy in conjunction with state-of-the-art electronic structure calculations. Based on these results, we establish that the ground state of this phase, arrived at by the chemical exfoliation of MoS2 using the usual Li intercalation technique, is a small gap (similar to 90 +/- 40 meV) semiconductor in contrast to most claims in the literature; we also identify the specific trigonal structure it has among many suggested ones.