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

TL;DR

This study explores the quantum Hall plateau transition in epitaxial graphene on SiC, revealing universal scaling behavior consistent with other graphene systems and providing insights into disorder effects at low temperatures.

Contribution

It demonstrates the quantum Hall plateau-plateau transition in epitaxial graphene and identifies a universal scaling exponent for the transition width.

Findings

Quantum Hall effect observed in epitaxial graphene.

Transition width scales as T^{-0.42} with temperature.

Universal behavior matches other graphene systems.

Abstract

We investigate the low-temperature magneto-transport properties of monolayer epitaxial graphene films formed on the Si-face of semi-insulating 4H-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 cm^2/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^{-\kappa} with exponent \kappa ~0.42. This universal scaling exponent agrees well with those found in III-V heterojunctions with short range alloy disorders and in exfoliated graphene.