Epitaxial graphene on SiC formed by the surface structure control technique

The thermal decomposition of silicon carbide (SiC) is a promising method for producing wafer-scale single-crystal graphene. The optimal growth condition for high-mobility epitaxial graphene fabricated by infrared rapid thermal annealing is discussed in this paper. The surface structures, such as step-terrace and graphene coverage structures, on a non-off-axis SiC(0001) substrate were well controlled by varying the annealing time in a range below 10 min. The mobility of graphene grown at 1620 ºC for 5 min in 100 Torr Ar ambient had a maximum value of 2089 cm2V-1s-1. We found that the causes of the mobility reduction were low graphene coverage, high sheet carrier density, and nonuniformity of the step structure

Carrier doping effect of humidity for single-crystal graphene on SiC

Carrier doping effects of water vapor and an adsorbed water layer on single-crystal graphene were evaluated. After annealing at 300 °C in nitrogen ambient, the sheet resistance of epitaxial graphene on a SiC substrate had a minimum value of 800 Ω/sq and the carrier density was estimated to be 1.2 × 1013 cm-2 for an n-type dopant. The adsorbed water layer, which acted as a p-type dopant with a carrier density of -7.4 × 1012 cm-2, was formed by deionized (DI) water treatment. The sheet resistances of graphene samples increased with humidity, owing to the counter doping effect. The estimated p-type doping amounts of saturated water vapor were -2.5 × 1012 cm-2 for DI-water-treated graphene and -3.5 × 1012 cm-2 for annealed graphene

Resistivity anisotropy measured using four probes in epitaxial graphene on silicon carbide

The electronic transport of epitaxial graphene on silicon carbide is anisotropic because of the anisotropy of the surface structure of the substrate. In this Letter, we present a new method for measuring anisotropic transport based on the van der Pauw method. This method can measure anisotropic transport on the macroscopic scale without special equipment or device fabrication. We observe an anisotropic resistivity with a ratio of maximum to minimum of 1.62. The calculated maximum mobility is 2876cm2·V-1·s-1, which is 1.43 times higher than that obtained by the standard van der Pauw method