On the electronic properties of defective graphene buffer layer on 6H–SiC(0001)

Abstract

Using first-principles calculations we predict that the electronic properties of graphene buffer layer (BL) on silicon carbide (SiC) can be modified by defect-induced itinerant states. Band structures and effective masses of single vacancy (SV), divacancy (DV) and Stone-Wales (SW) defective BL were calculated. Structural reconstruction at the vicinity of defects as well as spin polarization of silicon dangling bonds in the top bilayer SiC and nearby carbons from the BL, give rise to energetically degenerate magnetic states displaying electronic properties completely apart. This is particularly true for the SW and SV defective models where as many as three different magnetic states, turned out to be degenerate, either displaying a semiconductor nature or becoming half-metallic or even metallic. This is in contrast with previously reported results for the perfect BL (PBL) which suggested that most stable degenerate magnetic configurations share a semiconductor nature. On the other hand, for the DV system, the introduction of two vacancies in the BL causes loss of magnetism whereas a band gap of 0.54 eV is opened. Hole effective masses decay upon removal of one and two carbon atoms in the SV and DV systems where an increase in mobility is conceivable, provided current direction is carefully selected.