LUMINESCENCE DECAY TIME STUDIES AND TIME-RESOLVED CATHODOLUMINESCENCE SPECTROSCOPY OF CVD DIAMOND

Luminescence decay times of the characteristic electron-beam excited emission systems in CVD diamond were measured for samples grown by the combustion flame and microwave techniques. For the sharp emission lines between 2.3 and 3.0 eV the decay times range from 9.6 ns for the 2.33 eV line to 1.8 mus for the 2.537 eV line. The luminescence intensity of the 1.681 eV silicon-related system initially decreases relatively slowly, followed, after about 3 ns, by a rapid decrease with decay time of 2.4 +/- 0.3 ns. This behaviour is attributed to the presence of energy reservoirs coupled to the 1.681 eV excited state. The decay time of the blue band A is relatively short and this allows the bandshapes of vibronic systems superimposed on this band to be studied in more detail using time-resolved spectroscopy. In particular, the system with a zero-phonon fine at 2.99 eV is shown to have a different vibronic bandshape to the N3 system (with a zero-phonon line at 2.985 eV) with which it was originally confused. In favourable circumstances the sample-limited spectral resolution in continuously excited measurements is enhanced in the time-resolved spectra.