Tunable electronic and magnetic properties of graphene-like XYBe3 (XY = BN, AlN, SiC, GeC) nanosheets with carrier doping: a first-principles study

Abstract

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.