Influence of ageing on Raman spectra and the conductivity of monolayer graphene samples irradiated by heavy and light ions

The influence of long-term ageing (about one year) on the Raman scattering (RS) spectra and the temperature dependence of conductivity has been studied in two series of monolayer graphene samples irradiated by different doses of C$^{+}$ and Xe$^{+}$ ions. It is shown that the main result of ageing consists of changes in the intensity and position of D- and G- and 2D-lines in RS spectra and in an increase of the conductivity. The observed effects are explained in terms of an increase of the radius of the \textquotedblleft activated\textquotedblright{} area around structural defects.