Quantum-Hall plateau−plateau transition in top-gated epitaxial graphene grown on SiC (0001)

Abstract

We investigate the low-temperature magneto-transport properties of monolayer epitaxial graphene films formed on the Si-face of semi-insulating 4 H−SiC substrates by a high-temperature sublimation process. A high-k top-gate on the epitaxial graphene is realized by inserting a fully oxidized nanometer-thin aluminum film as a seeding layer, followed by an atomic layer deposition process. At low temperatures, the devices demonstrate a strong field effect by the top gate with an on/off ratio of ∼7 and an electron mobility up to ∼3250 cm2/Vs. After the observation of the half-integer quantum-Hall effect for monolayer epitaxial graphene films, detailed magneto-transport measurements have been carried out including varying densities, temperatures, magnetic fields, and currents. We study the width of the distinguishable quantum-Hall plateau to plateau transition (Landau level index n = 0 to n = 1) as temperature (T) and current are varied. For both gate voltage and magnetic field sweeps and T > 10 K, the transition width goes as T−κ with exponent k ∼ 0.42. This universal scaling exponent agrees well with those found in III−V heterojunctions with short-range alloy disorders and in exfoliated graphene.