Intriguing Electronic and Optical Properties of M2CX2 (M=Mo, W; X=O, F) MXenes and their van der Waals heterostructures

Abstract M 2 CX 2 (M=Mo,W; X=O,F) MXenes and their van der Waals heterostructures are investigated by first-principle calculations. Phonon spectrum has shown that Mo 2 CO 2 /W 2 CO 2 and Mo 2 CF 2 /W 2 CO 2 heterostructures and corresponding monolayers are dynamically stable. W 2 CO 2 exhibits the properties of topological insulator and Mo 2 CO 2 is narrow band gap semiconductor, while Mo(W) 2 CF 2 are metals. Mo 2 CO 2 /W 2 CO 2 heterostructure indicates a possible topological feature similar to corresponding monolayers and reveals type-II band alignment. Mo 2 CF 2 /W 2 CO 2 heterostructure generating n-type Schottky contact with 0.139eV barrier height. Large absorption in the visible region is observed for Mo 2 CO 2 and blue shift is noticed for W 2 CO 2 and W 2 CO 2 /Mo 2 CO 2 heterostructure, especially the part contributed by Mo 2 CO 2 .