Temperature dependent transfer characteristics of graphene field effect transistors fabricated using photolithography

We report on the temperature dependent transport characteristics of graphene field effect transistors (G-FETs) fabricated using photolithographic technique. Monolayer graphene layers were selected for the fabrication of electronic devices and the fabricated devices were further annealed in Ar/H-2 at 200 degrees C. The temperature dependence of resistance of the graphene flake shows semiconductor-type behavior. The resistance increases about one order of magnitude upon cooling from 300 K to 8 K. Our observations are good in agreement with the previously reported temperature behavior of monolayer graphene nanoribbons and reduced graphene oxide. A higher drain-current modulation in negative back-gate field with current minimum (the Dirac point) is observed at V-GS similar to -2.75 V. The carrier mobilities were determined from the measured transconductance and obtained mobilities are less than the conductivity and mobility of pristine graphene. The reason could be discussed in detail with variable range hopping mechanism which is consistent to our resistance/temperature data. (C) 2011 Elsevier B.V. All rights reserved.