Modulating the electronic structure and interface contact of WSe2/CrSe2 van der Waals heterostructures by strain engineering: Insights from first-principles calculations

As a recent member of the two-dimensional (2D) van der Waals (vdW) heterostructures, the $\mathrm{W}{\mathrm{Se}}_{2}/\mathrm{Cr}{\mathrm{Se}}_{2}$ heterostructure has received considerable attention due to its fascinating characteristics compared with the constituent 2D materials. In this paper, we performed first-principles calculations to investigate its structural, electronic, and magnetic properties and explored the effects of interlayer and in-plane strains on these properties. Our results reveal that the antiferromagnetic (AFM) ground state in the $\mathrm{Cr}{\mathrm{Se}}_{2}$ layer of the heterostructure is maintained owing to weak vdW interactions between the $\mathrm{Cr}{\mathrm{Se}}_{2}$ and $\mathrm{W}{\mathrm{Se}}_{2}$ layers. However, the AFM state can be transformed into the ferromagnetic state at interlayer compressive strain of \ensuremath{-}19% or in-plane tensile strain of 2.5%. Moreover, the $\mathrm{W}{\mathrm{Se}}_{2}/\mathrm{Cr}{\mathrm{Se}}_{2}$ heterointerface belongs to the metal-semiconductor interface and exhibits $p$-type ohmic contact and low contact resistance. The transition from $p$-type ohmic contact to $p$-type Schottky contact or $n$-type Schottky contact can be achieved by interlayer or in-plane strain engineering, which is associated with the strain-induced energy shifts of the valence band maximum and conduction band minimum of $\mathrm{W}{\mathrm{Se}}_{2}$. Additionally, the tunneling probability of the heterostructure rises dramatically (up to 100%) with interlayer coupling, which is favorable for carrier transport at the heterointerface. Our findings demonstrate that strain engineering is an effective way of modulating metal-semiconductor interfaces and provide theoretical guidance for designing electronic and magnetic devices based on the $\mathrm{W}{\mathrm{Se}}_{2}/\mathrm{Cr}{\mathrm{Se}}_{2}$ vdW heterostructure as well as broadening its applications in future functional devices.