Gate voltage and temperature dependent Ti-graphene junction resistance toward straightforward p-n junction formation

High-quality metal-graphene contact is crucial for the fabrication of high-performance graphene transistors. Although Ti has been widely used as metal electrodes in graphene-based devices owing to its excellent adhesive capability, contact resistance (R-c) for Ti/graphene (Ti/Gr) is typically high and varies largely by three orders of magnitude from similar to 10(3) to 10(6) Omega mu m. Here, we have systematically investigated the effects of gate voltage (V-G) and temperature (T) on R-c in the Ti/Gr interface. Besides significant V-G dependence, R-c in the n branch is always larger than that in the p branch, indicating a Ti induced n-doping in graphene. In addition, R-c exhibits an anomalous temperature dependence and drops significantly as the temperature decreases, reaching similar to 234 Omega mu m at 20 K. Such Ti/Gr contact can adjust the Fermi energy of up to 0.15 eV and can also directly form a well-defined sharp p-n junction without extra gates or chemical doping. These findings pave the way to develop the next generation of graphene-based electronic and optoelectronic devices. Published by AIP Publishing.