Tuning the electronic properties of HfSe$_2$/PtSe$_2$ heterostructure using electric field and biaxial strain

Herein, using the first-principles methods based on the density functional theory, the electronic properties of HfSe$_2$/PtSe$_2$ van der Waals heterostructures (vdWHs) and the influence of stacking patterns, interlayer coupling effect, biaxial strain, and external electric field have been investigated systematically.We found that the stacking patterns could modulate the types of band alignment: AA, AB$'$ and AC$'$ belong to type-II band alignment, whereas AB, AC, AA$'$ belong to type-I band alignment.Among these six stacking patterns, the AA stacking pattern was the most stable, with an interlayer distance of 2.87 A and a bandgap of 1.0 eV, and the type-II band alignment was beneficial for separating electron and hole carriers.Our calculations showed that the electronic properties of HfSe$_2$/PtSe$_2$ vdWHs could be effectively modulated via vertical strain and biaxial strains:an interesting transition from type-II to type-I band alignment was observed in HfSe$_2$/PtSe$_2$ vdWHs upon applying vertical or biaxial strains.Moreover, the bandgap of the designed heterostructure could be effectively modified through the compressive strain and interlayer coupling.Our findings will provide a theoretical basis for the potential applications of HfSe$_2$/PtSe$_2$ vdWHs designing of multifunctional electronic and optoelectronic devices.