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.

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