Tunable electronic and magnetic properties of graphene-like XYBe3 (XY = BN, AlN, SiC, GeC) nanosheets with carrier doping: a first-principles study
Utilizing first-principles calculations, we have systematically investigated the structural stabilities and electronic properties of XYBe3 (XY = BN, AlN, SiC, and GeC) nanosheets, which are isoelectronic analogues to the recently proposed Be3C2 nanosheet [B. Wang, et al., Nanoscale, 2017, 9, 5577]. These XYBe3 nanosheets have flat honeycomb lattice like graphene and can be viewed as amplified XY nanostructures with Be intercalation. Akin to their XY counterparts, the XYBe3 nanosheets also possess robust dynamical and thermal stabilities. All the four XYBe3 systems are nonmagnetic semiconductors, where the BNBe3 and AlNBe3 nanosheets have indirect band gaps while the SiCBe3 and GeCBe3 nanosheets have direct ones. Due to the elongated lattice by Be intercalation, the band gaps of the XYBe3 nanosheets are pronouncedly reduced compared to the pristine XY ones. Furthermore, their bands around the Fermi level are flat with small dispersions, thus inducing noticeable van Hove singularities near the band edges. As a result, either hole or electron doping can induce Stoner ferromagnetism in the XYBe3 nanosheets, which exhibit great energetic stabilities for the carrier-induced magnetism. More interestingly, the injected carriers can be fully spin-polarized and bring a half-metallic behavior into the XYBe3 nanosheets, where an intriguing bipolar spin-polarization phenomenon will be present. Our study demonstrates that these XYBe3 nanosheets possess peculiar electronic and magnetic properties, which will be promising nanomaterials for nano-electric and spintronic applications.