Layer-Dependent Chemically Induced Phase Transition of Two-Dimensional MoS2

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with layered structures provide a unique platform for exploring the effect of number of layers on their fundamental properties. However, the thickness scaling effect on the chemical properties of these materials remains unexplored. Here we explored the chemically induced phase transition of 2D molybdenum disulfide (MoS2) from both experimental and theoretical aspects and observed that the critical electron injection concentration required for the phase transition of 2D MoS2 increased with decreasing number of layers. We further revealed that the observed dependence originated from the layer-dependent density of states of 2H-MoS2, which results in decreasing phase stability for 2H-MoS2 with increasing number of layers upon electron doping. The layer-dependent phase transition of 2D MoS2 allows for the chemical construction of semiconducting-metallic hetero-phase junctions and subsequently, the fabrications of rectifying diodes and all 2D field effect transistors and thus opens new avenue for building ultrathin electronic devices. In addition, these new findings elucidate how electronic structures affect the chemical properties of 2D TMDCs and therefore, shed new lights on the controllable chemical modulations of these emerging materials.