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

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, M 2 O 3 , and MO 2 , 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 -Sc 2 O 3 , h -V 2 O 3 , and h -Mn 2 O 3 ; 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 -V 2 O 3 , 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.