Characteristic features of the magnetoresistance related to structured defects in graphene on SiC (0001)

Abstract

The structural characteristics of the graphene being grown on SiC (0001) were measured by Raman spectroscopy and Kelvin-probe microscopy. According to these data a single-layer graphene with a small amount (∼20%) of inclusions of double-layer islands with submicrometer dimensions was formed. Transport properties of graphitized silicon carbide are controlled by graphene layer heavily doped with electrons. In low magnetic fields at low temperatures, a negative magnetoresistance is observed due to the weak localization. A transition of the magnetoresistance from weak localization to weak antilocalization (the latter is a manifestation of the isospin in graphene and strong intervalley scattering ) was observed with increasing temperature (T > 150 K) for the first time in graphene grown on SiC (0001). The possible candidate for such intensive intervalley scattering can be the interphase boundaries separating the single-layered graphene and the islands of the double-layer graphene with high momentum transfer. A pronounced pattern of Shubnikov--de Haas oscillations was observed in strong magnetic fields (up to 30 T). This pattern demonstrates a 4-fold degeneration of the carrier spectrum due to the double spin degeneration and double valley degeneration and shows a manifestation of the Berry phase, which is somewhat different from the ‘ideal’ value of π.