Structure of Restacked MoS2 and WS2 Elucidated by Electron Crystallography

Abstract

There has been a lot of confusion about the nature of restacked MoS2 and WS2. The structure has been proposed to be trigonal TiS2 type with octahedral M4+ and called 1T-MoS2. The presence of a distortion in the metal plane that gives rise to a superstructure has been suggested. We have performed electron crystallographic studies on small (submicron) single crystal domains of restacked WS2 and MoS2 to solve their superstructure. We find that what initially seems to be a trigonal crystal is actually a “triplet” of three individual orthorhombic crystals. Using two-dimensional hk0 data from films for both “triple” and “single” crystals we calculated corresponding Patterson projections, which reveal a severe distortion in the Mo/W plane, forming infinite zigzag chains. The projection of the structure suggests M−M distances of 2.92 and 2.74 A for MoS2 and WS2, respectively. Least-squares refinement from the single-crystal data gives R1 = 13.3% for WS2 and R1 = 15.3% for MoS2. Therefore, we submit that restacked...