Strain engineering of Janus ZrSSe and HfSSe monolayers and ZrSSe/HfSSe van der Waals heterostructure

We investigated the effects of biaxial strain on electronic structure of ZrS2, ZrSe2, HfS2, HfSe2, ZrSSe and HfSSe monolayers. Similar to ZrS2, ZrSe2, HfS2, HfSe2 monolayers, Janus ZrSSe and HfSSe monolayers are indirect bandgap semiconductors. Tensile strain of 6(8)% transform ZrSSe(HfSSe) monolayer to direct bandgap semiconductor. Based on the calculation of binding energies and interlayer distance staking-(c) is found to be the most stable configuration for ZrSSe/HfSSe vdW heterostructure. Unstrained ZrSSe/HfSSe vdW heterostructure in staking-(c) is a type-II indirect bandgap semiconductor. Valence and conduction band edges show that under tensile strain ZrSSe, HfSSe and ZrSSe/HfSSe vdW heterostructure are efficient photocatalysts.