Optical characterization of some irradiation-induced centers in diamond

Photoluminescence (PL), PL excitation and optical absorption techniques wer e applied to the 3H, H3 and Si-related centers in natural and synthetic dia mond. Thresholds at 4.6 and 3.85 eV are observed in the excitation spectra: of the H3 and 3H luminescence, respectively. The 4.6-eV threshold could onl y be observed if single substitutional nitrogen (PI) centers were present i n The sample. It is ascribed to the ionization of the P1(+) centers followe d by an energy transfer from the P1 to the H3 centers. The energy transfer from other defects can also account for the temperature-independent PL, whi ch was observed from the 3H, H3, H4 and TR12' centers when they mere excite d at energies below the zero-phonon Line. Si-related centers are detected i n natural Ia diamond after neutron irradiation and annealing. Details of th e vibronic structure of the Si-V center in diamond grown by chemical vapor deposition are reported. (C) 2001 Elsevier Science B.V. All rights reserved .