We study the contact resistance and the transfer characteristics of back-gated field effect transistors of mono- and bi-layer graphene. We measure specific contact resistivity of ~ 7 k Ω μm2 and ~ 30k Ω μm2 for Ni and Ti, respectively. We show that the contact resistance is a significant contributor to the total source-to-drain resistance and it is modulated by the back-gate voltage. We measure transfer characteristics showing a double dip feature that we explain as the effect of doping due to charge transfer from the contacts causing minimum density of states for graphene under the contacts and in the channel at different gate voltage

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The relation between the electrical, chemical, and morphological properties of indium-tin oxide (ITO) thin films and organic light-emitting diode (OLED) performance is studied. We report on chemical (HCl, piranha solutions), thermal (vacuum annealing), physical (oxygen plasma, UV ozone), and combined treatments on ITO layers. The effects of these different treatments have been studied using the four-point probe resistivity measurement method, contact angle measurement, X-ray diffraction, surface profilometry, and UV-vis-IR transmittance. Double-layer OLEDs with treated ITO as the anode and poly(9,9-dihexyl-9H-fluorene-2,7diyl) and 8-hydroxyquinoline aluminum salt as the hole transporter and emitting material, respectively, have been realized. The electrical and optical properties of OLEDs have been extensively investigated, and it is shown that UV ozone-HCl combined treatment yields the highest hole injection efficiency and luminance and the lowest drive voltage. For each OLED with treated ITO, the anode potential barrier height decrease is estimated using Fowler-Nordheim and Schottky-Richardson modeling of the electrical conduction.