Electronic structures and band alignments of monolayer metal trihalide semiconductors MX3†
A series of new two-dimensional (2D) materials, metal trihalides MX3 (ScCl3, ScBr3, ScI3, YBr3, YI3, AsI3, SbI3, BiI3), have been explored by first-principles calculations. The relatively small cleavage energies compared with that of graphite indicate that monolayers of MX3 can be easily exfoliated from their layered bulk materials. Through electronic structure calculations, we find that monolayer metal trihalides are semiconductors with band gaps ranging from 2.82 eV (SbI3) to 5.47 eV (YBr3). Besides, the monolayers of AsI3, SbI3, and BiI3 display smaller electron effective mass, implying possibly larger electron mobility of these monolayers. Their band edges and band alignments have also been investigated for application in electronic devices. Our findings will expand the frontiers of new 2D materials and new applications for further research.