Dose and wavelength dependent study of graphene oxide photoreduction with VUV Synchrotron radiation

Photoreduction has so far received less attention than other approaches used to reduce graphene oxide (GO) like thermal and chemical reduction, although its potential is huge. The mechanism of deoxygenation is still questioned. In photolithographic applications, this means that one cannot predict whether the minimum feature size is close to the diffraction limit or larger. In this work we have studied GO photoreduction with vacuum ultraviolet Synchrotron radiation. GO has been exposed to extreme-UV and soft-X-ray radiation and the ratio between C-O and sp2 C-C bonds has been measured by photoemission spectroscopy as a function of dose and number of photons. The deoxygenation rate has been demonstrated to be proportional to the imaginary part f2 of the oxygen scattering factor. Experiments at the wavelengths where the f2 of oxygen is close to its maximum (namely close to 2 nm and between 20 nm and 60 nm) have demonstrated that GO can be rapidly reduced (even few minutes exposure time) with doses well below those needed for photothermal heating (the corresponding temperature rise is 1 lK) and without damaging the basal plane (the in-plane sp2 C-C bonds are not broken). Efficient nanometer scale GO photopatterning is therefore demonstrated to be possible.