Preliminary results obtained in as-grown and annealed CVD diamond using positron annihilation spectroscopy were reported. Clustering of as-grown vacancy defects upon annealing at above 1400C was observed. The optical activity of the vacancy defects was studied by irradiation with monochromatic light, in the visible range, during positron measurements.

Effects of Thermal Treatment on Optically Active Vacancy Defects in CVD Diamonds. J.M.Mäki, F.Tuomisto, C.Kelly, D.Fisher, P.Martineau: Physica B, 2007, 401-402, 613-6