Stability and electronic structure of hydrogen passivated few atomic layer silicon films: A theoretical exploration

The stability, electronic, and optical properties of two dimensional hydrogenated few atomic layer silicon (H-FLSi) are systematically studied with density functional theory calculations. The formation energy of H-FLSi decreases with increasing layer thickness and approaches zero at the thickness of double layer, suggesting that this material is energetically favorable and thus its experimentally synthesizing is feasible. Its bandgap decreases with the increase of the thickness and eventually approaches the value of bulk silicon. More interestingly, the bandgap of hydrogenated silicon films can be tuned by external electric field and even becomes metal. Importantly, the light absorption threshold and absorption peak of the H-Si mono-and bilayer locate in different energy regions and both move toward higher energy region as compared with those of the bulk silicon