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

Abstract

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 (VCH) 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–VCH 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 (EF) responsible for the large magnetic moment noted. The 1 charge doping (Li1 –VCH) further populates the occupied states in the band gap, shifting the EF towards the conduction band minimum. Consequently, the Li1 –VCH system possesses spintronic effects such as half-metallic ferromagnetic character and pronounced magnetism. The +1 charge doping (Li1+–VCH) 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 VCH defective graphane system and suggest a possible practical way of controlling it.