Strain-induced self-doping in silicene and germanene from first-principles

By first-principles calculations, the variations of band structures by strains are investigated for silicene and germanene nanosheets, i.e. the Si and Ge analogs of graphene. It is found that both systems exhibit a strain-induced self-doping phenomenon, which is closely related with their buckled structures and cannot arise in graphene. Under the compressive strain, the Dirac point is moved below the Fermi level, making the nanosheets behave as n-type doped. While under the tensile strain, the p-type doping is rendered by shifting the Dirac point above the Fermi level. Our studies demonstrate that the n-type/zero-band-gap/p-type semiconducting features can be switched for silicene and germanene by applying strains.