M2CX2 (M = Mo,W; X = O,F) MXenes and their van der Waals heterostructures are investigated by first-principle calculations. Phonon spectrum has shown that Mo2CO2/W2CO2 and Mo2CF2/W2CO2 heterostructures and corresponding monolayers are dynamically stable. W2CO2 exhibits the properties of topological insulator and Mo2CO2 is narrow band gap semiconductor, while Mo(W)2CF2 are metals. Mo2CO2/W2CO2 heterostructure indicates a possible topological feature similar to corresponding monolayers and reveals type-II band alignment. Mo2CF2/W2CO2 heterostructure generating n-type Schottky contact with 0.139 eV barrier height. Large absorption in the visible region is observed for Mo2CO2 and blue shift is noticed for W2CO2 and W2CO2/Mo2CO2heterostructure, especially the part contributed by Mo2CO2.
