Investigation of hydrogenated CVD diamond films by photo-thermal ionization spectroscopy

Different hydrogenated CVD diamond films as well as bulk IIb and IIa diamonds were investigated by means of photo-thermal ionization spectroscopy. All samples show a new photocurrent signal at temperatures lower than 120–20 K depending on the sample with a threshold around 100 meV what suggests a presence of shallow levels on the hydrogenated diamond surface. The photocurrent spectrum due to these shallow levels consists of features similar to the two-phonon absorption in diamond. Influence of annealing in air on the photocurrent behavior was investigated as well.