Direct observation of hydrogen-related luminescent states in subsurface region of homoepitaxial diamond films

We found hydrogen-related luminescence in the subsurface region of chemical vapor deposited homoepitaxial diamond films by means of cathodoluminescence. A specific broad peak at around 540 nm is observed in the hydrogenated films, but not in the conventional oxidized films. The gap states related to the peak observed at around 540 nm are found to exist spatially in the surface region. The fact is consistent with the hydrogen distribution previously determined by secondary ion mass spectroscopy. The result indicates the existence of hydrogen-related luminescent states in the subsurface region of as-deposited homoepitaxial diamond films.