Strain and Electric Field Engineering of G-ZnO/SnXY (X, Y = S, Se) S-Scheme Heterostructures for Photocatalyst and Electronic Device Applications: A Hybrid DFT Calculation

Using hybrid density functional theory calculations, we systematically study the biaxial strain and electric field modulated electronic properties of g-ZnO/SnS 2, g-ZnO/SnSe 2, and g-ZnO/SnSSe S-scheme van der Waals heterostructures (vdWHs). g-ZnO/SnS 2 and g-ZnO/SnSSe are found to be promising photocatalysts for water splitting with high solar-to-hydrogen efficiencies, even under acidic, alkaline, and high-stress conditions. The strain effect on the bandgaps of g-ZnO/SnXY is explained in detail according to the correlation between geometry structure and orbital hybridization of SnXY, which could help understand the strain-induced band structure evolutions in other SnXY (X, Y = S, Se)-based vdWHs. It is surprising that under an external electric field, g-ZnO/SnS 2, g-ZnO/SnSe 2, and g-ZnO/SnSSe can offer the occupied nearly free-electron (NFE) states. In many materials, NFE states are usually unoccupied and is not conducive to the charge transport. The NFE state in g-ZnO/SnSe 2 is the most sensitive to the electric field and might be promising electron transport channel in nanoelectronic devices. g-ZnO/SnSe 2 might also have application potential in gas sensors and high-temperature superconductors.