Chemical exfoliation of MoS2 leads to semiconducting 1T' phase and not the metallic 1T phase

TL;DR

This study reveals that chemically exfoliated MoS2 predominantly exhibits a semiconducting 1T' phase with a small band gap, challenging the common belief that it is metallic 1T, based on combined spectroscopy and electronic structure calculations.

Contribution

The paper provides the first direct experimental evidence that the chemically exfoliated MoS2's trigonal phase is a semiconducting 1T' phase, not the metallic 1T phase as previously thought.

Findings

Chemically exfoliated MoS2 has a small band gap (~90 meV)

The identified phase is the semiconducting 1T' structure

This challenges the common assumption of a metallic 1T phase in exfoliated MoS2

Abstract

A trigonal phase existing only as small patches on chemically exfoliated few layer, thermodynamically stable 1H phase of MoS2 is believed to influence critically properties of MoS2 based devices. This phase has been most often attributed to the metallic 1T phase. We investigate the electronic structure of chemically exfoliated MoS2 few layered systems using spatially resolved (lesser than 120 nm resolution) photoemission spectroscopy and Raman spectroscopy in conjunction with state-of-the-art electronic structure calculations. On the basis of these results, we establish that the ground state of this phase is a small gap (~90 meV) semiconductor in contrast to most claims in the literature; we also identify the specific trigonal (1T') structure it has among many suggested ones.