Small-field dosimetry based on reduced graphene oxide under MeV helium beam irradiation

A new type of ion dosimeter based on graphene oxide (GO) foils is presented and discussed. GO is biocompatible, stable, tissue equivalent and has special chemical and physical properties. The ion irradiation reduces the material thanks to the breaking of oxygen functional groups bonded to the carbon matrix and to the consequent their desorption. The reduction effect increases the carbon-to-oxygen atomic ratio and transforms the pristine insulator GO into the semiconductive reduced GO (rGO). The reduction increases with the ion dose making the material more electrically conductive, decreasing its band gap and making it denser. At high doses of 2 MeV helium beam irradiation, the electrical conductivity increases linearly with the ion fluence for values within 1011 and 5 × 1014 ions/cm2, corresponding to absorbed doses of 25.9 kGy and 129.55 MGy, respectively. The results indicate that this material reduction is controllable through the desorption of oxygen groups and absorbed hydrogen, by the increment of the electrical conductivity and by the surface roughness, all these parameters depending on the absorbed dose by the material, which can be a good candidate to realise small ion dosimeters, especially to be used in the small-field dosimetry.