Ab initio Study of Tunable Band Gap of Monolayer and Bilayer Phosphorene by the Vertical Electronic Field

Using the ab initio plane-wave ultrasoft pseudopotential method based on generalized gradient approximation（GGA）,we investigated the band-gap tuning in monolayer phosphorene（MLP） and bilayer phosphorene（BLP） by external electric fields applied perpendicular to the layers.The band continuously decreases with increasing applied electric fields,eventually rendering them metallic.For MLP,the phenomenon is explained in the light of the giant Stark effect,which is essentially characterized by the interlayer spacing,for the rate of change of bandgap with applied external field.The atomic distance and charges also contribute to the semiconductor-metal transition.The BLP is more sensitive to electric fields than MLP,since their charges are rearranged among bilayers and the bandgap can dramatically drop in terms of electronic field.The results show the bandgap will change for the fabrication of novel electronic and photonic devices.