Thermal stability and electronic and magnetic properties of atomically thin 2D transition metal oxides

Abstract

Two-dimensional (2D) transition metal oxides (TMOs) are an emerging class of nanomaterials. Using density functional theory and ab initio molecular dynamics (AIMD) simulations, we carried out a systematic study of atomically thin metal oxide phases with compositions MO, M2O3, and MO2, for transition metal elements Sc, Ti, V, Cr, and Mn. We identified nine thermally stable structures that may be realized as free-standing nanosheets: hexagonal h-Sc2O3, h-V2O3, and h-Mn2O3; hexagonal t-VO, t-CrO, and t-MnO; and square sq-TiO, sq-VO, and sq-MnO. The t-MO phases are novel hexagonal structures which emerged naturally from phase transformations observed during AIMD simulations. The 2D TMOs were found to exhibit a wide range of remarkable electronic and magnetic properties, indicating that they are bright candidates for electronic and spintronic applications. Most exceptional in this regard is h-V2O3, that is the only phase that has been experimentally realized so far, and was found to be a ferromagnetic half-metal with Dirac-cone-like bands.