Local phase transition at crack edges of Mo1-xWxTe2 polymorphs

Abstract

The phase engineering of two-dimensional (2D) materials has attracted considerable attention in recent years, but nanometer-scale samples and experimental techniques have limited the rigorous study of the local phase engineering of 2D atomic crystals. Here, we report on a nanometer-scale probe of phase evolution in the Mo1-xWxTe2 alloys, which exhibit a structural transition between the semiconducting 2H phase and the metallic 1T(sf)phase. We found that many crack edges are created by the accumulated tungsten atoms, resulting in poor crystallinity in the 2H-Mo1-xWxTe2 flakes at the vicinity of phase transition with a tungsten content, x = 0.08. With mild laser irradiation of the 2H-Mo1-xWxTe2 flakes, the 2H phase region near a crack edge was easily converted to the 1 degrees T-sf phase, while other areas apart from the crack edge region retained their 2H phase under the same laser treatment. Our study clarifies the role of locally accumulated atoms and crystallinity for the phase engineering of 2D materials, which opens the way to various applications based on heterophase structures, ranging from energy conversion and storage to optoelectronic devices.