Elucidating the electronic and magnetic properties of epitaxial graphene grown on SiC with a defective buffer layer

Abstract

The epitaxial graphene layer (EG) grown on silicon carbide (SiC) is severely affected by the presence of the underlying graphene buffer layer (BL). However, little information is available on the alteration of the magnetic and electronic properties of the top layer when the BL presents structural defects. Herein, by means of first-principle density functional calculations, we investigate the electronic and magnetic properties of the SiC–BL–EG system, with a single vacancy, divacancy or a Stone–Wales defective buffer layer. Our results indicate that new highly stable magnetic states are observed in the SiC–BL–EG non-defective and defective systems, as compared to the SiC–BL models. In addition, the energy differences among the degenerate magnetic states originally found in the SiC-defective systems are further reduced upon inclusion of the EG layer. Interestingly, for the single-vacancy system, a p-type doping is noticed in the spin down channel of the M = 4 µB configuration. This is in sharp contrast with the n-type doping generally measured for EG. Moreover, charge neutrality was observed in two cases namely, the half-semimetal ferromagnetic configurations of the non-defective and the single-vacancy systems. This result may open new avenues to control the electronic doping of the epitaxial graphene layer via defect engineering.