Scaling in the quantum Hall regime of graphene Corbino devices

The scaling behavior of graphene devices in Corbino geometry was investigated through temperature dependent conductivity measurements under magnetic field. Evaluation of the Landau level width as a function of temperature yielded a relatively low temperature exponent of k = 0.16 +/- 0.05. Furthermore, an unusually large value close to 7.6 +/- 0.9 was found for the universal scaling constant gamma, while the determined inelastic scattering exponent of p = 2 is consistent with established scattering mechanisms in graphene. The deviation of the scaling parameters from values characteristic of conventional two-dimensional electron gases is attributed to an inhomogeneous charge carrier distribution in the Corbino devices. Direct evidence for the presence of the latter could be gained by spatially resolved photocurrent microscopy away from the charge neutrality point of the devices. (C) 2014 AIP Publishing LLC.