Atomic-scale dynamics of the phase transition in bilayer PtSe2

Abstract

Understanding the mechanism of phase transition is of great importance for modulating the physical properties and realizing the potential applications of two-dimensional (2D) materials. Herein, by performing in situ experiments in an atomic resolution scanning transmission electron microscope (STEM), it is found that the 2H → 1T and 2H → N phase transition can be observed in bilayer PtSe₂ under electron beam irradiation. The phase transition can be tracked in real time which enables in-depth analysis of the transformation mechanism. It is revealed that both interlayer and intralayer gliding occurred during the transition process in bilayer PtSe₂. In addition, the intralayer shift requires a longer electron beam irradiation time to complete due to the stronger intralayer covalent bond strength. These mechanistic insights may provide a fundamental understanding for development and optimization of PtSe₂.