▎ 摘　　要

The effect of vacuum annealing followed by exposure to oxygen and water vapor on the unintentional doping of CVD-grown graphene was investigated. CVD graphene samples were cycled between room temperature and 500 degrees C in vacuum while in situ Raman measurements were recorded. During the heating and cooling cycle, a hysteresis in the Raman response due to the desorption of p-dopants was observed. Upon exposure to O-2 gas or air, a blue shift in the Raman response with respect to the as grown film was observed which was due to increased adsorption of p-dopants on the sample. Experiments showed that a combination of water vapor and oxygen is more effective in p-doping the samples than just oxygen and that the doping effects are reversible in both cases. Electrical measurements performed on back-gated field effect graphene devices indicate that shifts in the Dirac point correlate well to the shifts in the Raman peak positions as well as changes found in XPS and Kelvin Probe measurements, verifying the changes in doping of the graphene. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4731472]