Résumé
The ultimate surface exposure provided by graphene makes it the ideal sensor platformbut also exposes its intrinsic properties to any environmental perturbations. Ramanspectroscopy has been used here to demonstrate the influence of the laser power and thesurface chemistry of the SiO2/Si substrate on the charge carrier density of exfoliatedgraphene in air. It is shown that the charge carrier density of graphene exfoliated on aSiO2/Si substrate can be finely and reversibly tuned between hole (p-type) and electron(n-type) doping, across neutral state (i-type) with visible photons. This effect issignificantly affected by the substrate cleaning method and completely suppressed insuspended graphene. The observed phenomenon has a subsecond characteristic time anddoes not involve the chemical modification of graphene.One technical implication of our study for the entire scientific community using Ramanspectroscopy of graphene as a routine characterization technique is that it should beconsidered as potentially invasive as far as electronic properties are concerned. On theother hand, the ability to tune the charge carrier density with visible photons opens awide set of opportunities to develop optically gated graphene electronic devices and anew approach to graphene optoelectronics. Finally, this effect should allow studying theinterplay between graphene properties and the environment and triggering laser-assistedfunctionalization of graphene leading to more advanced devices.[1] A. Tiberj, M. Rubio-Roy, M. Paillet, J.-R. Huntzinger, P. Landois, M. Mikolasek,S. Contreras, J.-L. Sauvajol, E. Dujardin, A.-A. Zahab, Scientific Reports, 3, 2355(2013).