Emergent properties resulting from type-II band alignment in a new lateral (a-PbO/a-SnO) heterostructure

a-PbO and a-SnO monolayers are stable nanostructures that are separately synthesized by epitaxial growth on the same oxidized silicon substrate (SiO2/Si). In this study, we theoretically designed new (a-PbO)m/(a-SnO)(m) lateral heterostructures formed by periodically repeating narrow PbO and SnO strips joined along their adjacent one-dimensional interface. By means of first-principles calculations, structural, mechanical and electronic properties are investigated for different widths (from m = 1 to m = 10). Interface and mechanical stability of these heterostructures are demonstrated from m = 1 to m = 8. The advantage of heterostructures of this kind is that their band gaps can be adjusted by variation of their width, which may provide new opportunities for ultimate band gap engineering at the nanoscale and for new applications. Electronic calculations for the (a-PbO)(7)/(a-SnO)(7) heterostructure show that it has an Anderson type-II band alignment, where the conduction band minimum and valence band maximum are located separately at PbO and SnO strips, respectively. Consequently, the photon-generated electron-hole pairs spatially separated, resulting in much a longer exciton lifetime than in the two monolayers separately, which needs to be confirmed by further experimental measurements.