Polar discontinuities and interfacial electronic properties of Bi2O2Se on SrTiO3

The layered oxychalcogenide semiconductor ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}\mathrm{Se}$ (BOS) hosts a multitude of unusual properties including high electron mobility. Owing to similar crystal symmetry and lattice constants, the perovskite oxide ${\mathrm{SrTiO}}_{3}$ (STO) has been demonstrated to be an excellent substrate for wafer-scale growth of atomically thin BOS films. However, the structural and electronic properties of the BOS/STO interface remain poorly understood. Here, through first-principles study, we reveal that polar discontinuities and interfacial contact configurations have a strong impact on the electronic properties of ideal BOS/STO interfaces. The lowest-energy [$\mathrm{Bi}\text{\ensuremath{-}}{\mathrm{TiO}}_{2}$] contact type, which features the contact between a ${\mathrm{Bi}}_{2}{\mathrm{O}}_{2}$ layer of BOS with the ${\mathrm{TiO}}_{2}$-terminated surface of STO, incurs significant interfacial charge transfer from BOS to STO, producing a BOS/STO-mixed, $n$-type metallic state at the interface. By contrast, the [Se-SrO] contact type, which is the most stable contact configuration between BOS and SrO-terminated STO substrate, has a much smaller interfacial charge transfer from STO to BOS and exhibits $p$-type electronic structure with no interfacial hybridization between BOS and STO. These results indicate that BOS grown on ${\mathrm{TiO}}_{2}$-terminated STO substrates could be a fruitful system for exploring emergent phenomena at the interface between an oxychalcogenide and an oxide, whereas BOS grown on SrO-terminated substrates may be more advantageous for preserving the excellent intrinsic transport properties of BOS.