CVD grown graphene field-effect device arrays with water top gate

We synthesize single-layer graphene sheets by chemical vapor deposition (CVD) on copper foil. Large sheets are transferred to Si/SiO$_{2}$ wafers using poly(methyl methacrylate) (PMMA). Raman spectroscopy of transferred graphene shows the signatures of high-quality graphene with a very small D band. Graphene field-effect device arrays are fabricated using conventional photolithography. A thin SiO$_{2}$ film is deposited on top of the finished devices as the last step. We employ two methods of field effect gating. Gate sweeps of the SiO$_{2}$ back gate show large initial hole doping. When a droplet of water is deposited on the device and used as a top gate, the majority of devices show a Dirac point of $\sim$0.3 V and bipolar behavior. The water top gate injects charges much more efficiently than the 290nm SiO$_{2}$ back gate. The mobility of the devices is estimated to be a few thousand cm$^{2}$/Vs. We discuss transport properties and potential applications of these device arrays.