Formation and relaxation of hydrogen-related defects in the subsurface region of diamond films

We report the metastability of hydrogen-related defects in hydrogen-plasma-treated diamond films. In the cathodoluminescence spectra, a specific broad peak at around 2.3 eV is observed in the subsurface region of the diamond films treated at 800 degrees C. The peak is not observed in those treated below 500 degrees C; however, it suddenly appears after low-energy (similar to 10 kV) electron beam irradiation. Corresponding to this phenomenon, the irradiation also leads to a decrease in the sheet resistance of the films. These results indicate the existence of a metastable configuration of hydrogen-related defects, which relaxes by the low-energy electron beam irradiation.