Reduction of metal contact resistance of graphene devices via CO2 cluster cleaning

We report on a cleaning technique using CO2 clusters for large-scale mono-layer graphene fabricated via chemical vapor deposition (CVD) and its application to reduce contact resistance of the CVD graphene device. We found that polymeric residues, i.e., polymethyl methacrylate and photoresist which are generated during transfer and patterning of graphene, can be effectively removed via rapid shrinkage, induced by thermal energy transfer to low temperature CO2 clusters. By applying the CO2 clusters to the cleaning of the interface between metal and graphene, the metal contact resistance of the fabricated graphene field effect transistor was lowered to 26.6% of pristine graphene. The contact resistance shows the best result at an optimized CO2 cluster cleaning condition with a flow rate of 20 l/min, and the resistance was further lowered to 270 Omega mu m when a gate bias of -40V was applied. We expect that the proposed CO2 cluster cleaning to be a very promising technique for future device application using 2-dimensional materials, as it can enable low-energy, large-area, high-throughput, and mass-production-compatible process. (C) 2014 AIP Publishing LLC.