Evaluation of conductivity in graphitized CVD-grown diamonds by Raman micro-spectroscopy

Graphite has been often used as an electrode for batteries due to its resistance to corrosion and good electrical conductivity. Graphite electrodes was obtained by modifying the surface of a synthetic diamond substrate, but the uniformity of the graphitized area on the surface should be monitored. Hall measurement was generally used to evaluate the performance of electrodes, but it can only provide the average conductivity between the electrodes. In this study, we performed Raman scattering micro-spectroscopy to evaluate the conductivity of graphite with non-destructive, noncontact measurements and the high spatial resolution. The samples in this study was graphitized from CVD-grown diamond by thermal treatment with deposition of the catalytic metal Nickel. Raman spectra were measured in the Ni-deposited and non-Ni-deposited regions, and it can be seen that only the catalytically reacted area was graphitized from diamond. The sample with graphite-derived peaks in Raman spectrum also showed symmetrical voltamogram in electrolysis measurements. However, for the samples with insufficient modification to graphite, the electrolysis voltamogram were asymmetric. It was possible to predict the properties of the redox reaction between the electrode and the solution in electrochemistry from the Raman spectra. These results verify the production of graphite-diamond hybrid electrodes.