Reversible optical doping of graphene
Résumé
The ultimate surface exposure provided by graphene makes it the ideal sensor platform
but also exposes its intrinsic properties to any environmental perturbations. Raman
spectroscopy has been used here to demonstrate the influence of the laser power and the
surface chemistry of the SiO2/Si substrate on the charge carrier density of exfoliated
graphene in air. It is shown that the charge carrier density of graphene exfoliated on a
SiO2/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 is
significantly affected by the substrate cleaning method and completely suppressed in
suspended graphene. The observed phenomenon has a subsecond characteristic time and
does not involve the chemical modification of graphene.
One technical implication of our study for the entire scientific community using Raman
spectroscopy of graphene as a routine characterization technique is that it should be
considered as potentially invasive as far as electronic properties are concerned. On the
other hand, the ability to tune the charge carrier density with visible photons opens a
wide set of opportunities to develop optically gated graphene electronic devices and a
new approach to graphene optoelectronics. Finally, this effect should allow studying the
interplay between graphene properties and the environment and triggering laser-assisted
functionalization 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).