Li states on a C-H vacancy in graphane: a first-principles study

Using a hybrid density functional theory approach, we have studied the effect of the interaction of a Li atom with a C-H pair vacancy defect (V-CH) in a graphane monolayer on the thermodynamic stability, structural, magnetic and electronic properties, taking into account the effect of charge doping. We found that a Li atom and charge doping enhanced the thermodynamic stability of a VCH defective graphane monolayer. The Li-V-CH system may likely act as a single deep donor, and can readily compensate the acceptor. The effects of Li introduce more occupied states in the band gap, and there exists strong hybridization between the C 2p states and Li 2s states at the vicinity of the Fermi level (E-F) responsible for the large magnetic moment noted. The -1 charge doping (Li1--V-CH) further populates the occupied states in the band gap, shifting the EF towards the conduction band minimum. Consequently, the Li1--V-CH system possesses spintronic effects such as half-metallic ferromagnetic character and pronounced magnetism. The +1 charge doping (Li1+-V-CH) removes some of the Li induced occupied states, slightly shifting the EF towards the valence band maximum leading to a reduction in the magnetic moment. Our findings give an explanation of the origin of magnetism in a V-CH defective graphane system and suggest a possible practical way of controlling it.