during the
laser switch on and off. Compared to studies in literature that
report increasing resistivity of graphene over temperature [6-
8], we measured a decrease in resistivity that consequently
increases the conductivity when the laser source is on. Our
hypothesis is that the increase of resistivity because of the
temperature rise is largely compensated by its decrease under
IR laser. Thus photon effect should be discussed.
We further analyzed the absorbed IR gated transport
behavior. The notion of normalized change of IR reflectivity -
δR/R versus photon energy for a representative graphene
monolayer and bilayer can be applied. Note that -δR/R is
related to the complex optical conductivity σ (ω) of graphene
through the relation