In situ edge engineering in two-dimensional transition metal dichalcogenides

Xiahan Sang, Xufan Li, Wen Zhao, Jichen Dong, Christopher M. Rouleau, David B. Geohegan, Feng Ding, Kai Xiao, & Raymond R. Unocic , 2018
Fusion TEM holder tip
Image courtesy of Nature Communications

Abstract

Exerting synthetic control over the edge structure and chemistry of two-dimensional (2D) materials is of critical importance to direct the magnetic, optical, electrical, and catalytic properties for specific applications. Here, we directly image the edge evolution of pores in Mo1-xWxSe2 monolayers via atomic-resolution in situ scanning transmission electron microscopy (STEM) and demonstrate that these edges can be structurally transformed to theoretically predicted metastable atomic configurations by thermal and chemical driving forces. Density functional theory calculations and ab initio molecular dynamics simulations explain the observed thermally induced structural evolution and exceptional stability of the four most commonly observed edges based on changing chemical potential during thermal annealing. The coupling of modeling and in situ STEM imaging in changing chemical environments demonstrated here provides a pathway for the predictive and controlled atomic scale manipulation of matter for the directed synthesis of edge configurations in Mo1-xWxSe2 to achieve desired functionality.

Impact Statement

There is incredible potential for atomistic imaging of 2D materials in situ and we can utilize nano hetero-structures for electronic and magnetic properties.