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.

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