A first principle calculation of electronic and dielectric properties of electrically gated low-buckled mono and bilayer silicene

The structural, electronic and dielectric properties of mono and bilayer buckled silicene sheets are investigated using density functional theory. A comparison of stabilities, electronic structure and effect of external electric field are investigated for AA and AB-stacked bilayer silicene. It has been found that there are no excitations of electrons i.e. plasmons at low energies for out-of-plane polarization. While for AB-stacked bilayer silicene 1.48 eV plasmons for in-plane polarization is found, a lower value compared to 2.16 eV plasmons for monolayer silicene. Inter-band transitions and plasmons in both bilayer and monolayer silicene are found relatively at lower energies than graphene. The calculations suggest that the band gap can be opened up and varied over a wide range by applying external electric field for bilayer silicene. In infra-red region imaginary part of dielectric function for AB-stacked buckled bilayer silicene shows a broad structure peak in the range of 75–270 meV compared to a short structure peak at 70 meV for monolayer silicene and no structure peaks for AA-stacked bilayer silicene. On application of external electric field the peaks are found to be blue-shifted in infra-red region. With the help of imaginary part of dielectric function and electron energy loss function effort has been made to understand possible interband transitions in both buckled bilayer silicene and monolayer silicene.