Epitaxial graphene surface preparation for atomic layer deposition of Al2O3

Abstract

Atomic layer deposition was employed to deposit relatively thick (∼30 nm) aluminum oxide (Al2O3) using trimethylaluminum and triply-distilled H2O precursors onto epitaxial graphene grown on the Si-face of silicon carbide. Ex situ surface conditioning by a simple wet chemistry treatment was used to render the otherwise chemically inert graphene surface more amenable to dielectric deposition. The obtained films show excellent morphology and uniformity over large (∼64 mm2) areas (i.e., the entire sample area), as determined by atomic force microscopy and scanning electron microscopy. X-ray photoelectron spectroscopy revealed a nearly stoichiometric film with reduced impurity content. Moreover, from capacitance-voltage measurements a dielectric constant of ∼7.6 was extracted and a positive Dirac voltage shift of ∼1.0 V was observed. The graphene mobility, as determined by van der Pauw Hall measurements, was not affected by the sequence of surface pretreatment and dielectric deposition.