Strain-induced superstructure evolution and Te vacancy accumulation in AgTe monolayer grown on Ag(111) substrate

Abstract

Two-dimensional (2D) materials have attracted increasing attention for frontier science and industrial applications in the past few decades. As a 2D materials with honeycomb lattice, AgTe monolayer grown on Ag (111) substrate belongs to the transition metal monochalcogenides (TMMs) family possessing various superstructures and exotic electronic structure. In this report, the AgTe monolayer superstructure is mainly studied using scanning tunneling microscope/spectroscopy (STM/S) measurements. With the increase of Te deposition, the planar structure of the AgTe monolayer becomes the one-dimensional (1D) moiré pattern structure, which transformation is related to the change of strain combing with theoretical analysis. When there is an isotropic strain on the surface, the AgTe monolayer is a flat honeycomb structure. In contrast, the lattice structural strain is released under a uniaxial strain as the AgTe monolayer is transformed into a 1D moiré pattern structure. In addition, Te vacancies in the AgTe monolayer are also affected by the synergistic effect of strain and Ag (111) substrate, and the concentration of Te vacancy changes significantly with the strain transformation. Moreover, both experimental statistics and theoretical calculations verify that Te vacancy tend to appear in the bright ridge (BR) region of the AgTe monolayer with a 1D moiré pattern structure, which is also the result of strain modulation. Our findings open up a new thought for strain transformation control of 2D materials driven by elemental concentration.