Graphene p-Type Doping and Stability by Thermal Treatments in Molecular Oxygen Controlled Atmosphere

Doping and stability of monolayer low defect content graphene transferred on a silicon dioxide substrate on silicon are investigated by micro-Raman spectroscopy and atomic force microscopy (AFM) during thermal treatments in oxygen and vacuum controlled atmosphere. The exposure to molecular oxygen induces graphene changes as evidenced by a blue-shift of the G and 2D Raman bands, together with the decrease of I-2D/I-G intensity ratio, which are consistent with a high p-type doping (similar to 10(13) cm(-2)) of graphene. The successive thermal treatment in vacuum does not affect the induced doping showing this latter stability. By investigating the temperature range 140-350 degrees C and the process time evolution, the thermal properties of this doping procedure are characterized, and an activation energy of similar to 56 meV is estimated. These results are interpreted on the basis of molecular oxygen induced similar to 10(13) cm(-2) p-type doping of graphene with stability energy >49 meV and postdoping reactivity in ambient atmosphere due to reaction of air molecules with oxygen trapped between graphene and substrate.