  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.
