Photoluminescence in CVD diamond films

Photoluminescence (PL) measurements of CVD diamond films reveal well-defined lines at 1.68, 1.945 and 2.156 eV, in addition to broad red, green and blue bands. The 1.68 eV line is attributed to Si-related center and when accompanied by the red band, shows a strong dependence of its intensity on the excitation photon energy. The 2.156 and 1.945 eV lines are assigned to nitrogen-vacancy complexes. The absence of the 1.945 eV line for samples with low nitrogen content shows that the formation of the 2.156 eV center is more favorable than of the 1.945 eV center. Blue, green and red broad PL bands are attributed to dislocations, boron-related defect and to nitrogen, respectively. Results on intensity and excitation photon energy dependences of PL measured for CVD and shock-synthesis diamond showed that a donor-acceptor recombination model cannot explain the broad band PL in our samples.