Polar discontinuities and interfacial electronic properties of Bi2O2Se on SrTiO3

The layered oxychalcogenide semiconductor Bi2O2Se (BOS) hosts a multitude of unusual properties including high electron mobility. Owing to similar crystal symmetry and lattice constants, the perovskite oxide SrTiO3 (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 [Bi-TiO2] contact type, which features the contact between a Bi2O2 layer of BOS with the TiO2-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 TiO2-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.