Cathodoluminescence decay time studies of the neutral vacancy in diamond

Abstract

The decay of GR1 cathodoluminescence associated with the neutral vacancy in diamond has been studied in the temperature range 10 to 77 K. Exponential decay of the luminescence is only obtained when short (5 ns) widely spaced (10 mu s) pulses are used, yielding a decay time of 3.1 ns in the temperature range studied. If much longer excitation pulses are used (10 mu s at 10 kHz), or a higher duty cycle (100 ns at 1 MHz), additional structure is observed in the zero-phonon region of the luminescence spectrum identical with that obtained using continuous excitation. Under these conditions the luminescence decay is slower and non-exponential. The value of 3.1 ns, obtained using short widely spaced pulses, is therefore expected to represent the upper limit for the radiative decay time of the centre, and compares with a decay time of 2.55 ns obtained using photo-excitation. Differences between the cathodoluminescence and photoluminescence spectra, and the complex decay of the former, are attributed to the indirect excitation mechanism, rather than to saturation effects.