Point Defect Stability and Dielectric Properties of Graphene-Like Monolayer Materials

Atomically thin two-dimensional (2D) materials have attracted tremendous interest and shown great potential in various research areas of modern nanotechnology. Here, we systematically study a category of 2D families, namely, graphene-like monolayer monoxides, monochlorides, and mononitrides (GLMMs), by virtue of density functional theory and density functional perturbation theory. First, the stability of different native point defects in GLMMs is investigated energetically, and the results show that most vacancy defects, especially the neutral nonmetal atom vacancies, possess high formation energy, manifesting their outstanding structural stability and high resistance to vacancy formation during the preparation process. The ab initio molecular dynamics also confirm the thermal stability of these GLMMs with and without defects. Subsequently, their dielectric properties are explored by the effective dielectric model (EDM) and 2D electronic polarizability simultaneously for comparison. It is found that most GLMMs possess far higher out-of-plane dielectric constants than h-BN, behaving as promising monolayer materials for device applications. Moreover, 2D electronic polarizability is proven to exhibit a significant advantage in evaluating the dielectric property of 2D materials with an atomically thin layer over the EDM method, owing to the sensitivity of the EDM on the layer thickness. All theoretical calculation results provide a comprehensive prediction of the atomic structures and dielectric properties of GLMMs, aiming to facilitate the synthesis and further application of such novel 2D materials.