Hydrogenated ψ-graphene: Band gap engineering and optical properties

Hydrogen passivation was predicted to be an effective method to open the band gap of psi-graphene by the density functional theory calculations. A critical H coverage of similar to 60% was found, above which the hydrogenated psi-graphene opens a band gap. The band gap can be tailored within a wide range of 0-3.57 eV by changing the H coverage. Meanwhile, the opened band gap brings the hydrogenated psi-graphene different optical properties from the pristine psi-graphene. Generally, the w-graphene possesses the major absorption peaks similar to graphene, except for the redshift of sub-pi peak features caused by the pentagons and heptagons. However, hydrogen passivation can result in quite different optical properties from the pristine psi-graphene for both the absorption peaks and delay. As the H coverage decreases, the absorption coefficient of the hydrogenated psi-graphene drops independently on the light polarization. Particularly, the absorption delay will be improved during removing the H atoms due to lowering of band gap, which is useful for selective optical absorption.