Abstract
A technique previously employed to investigate photochromic effects in 4H SiC has now been applied to various high pressure and high temperature (HPHT) and chemical vapour deposition (CVD) diamond samples. After electron irradiation with 250–300keV electrons the irradiated region is first investigated for uniformity of defects created by low-temperature (7K) microscopic photoluminescence (PL) using a 488nm laser. It is then subjected to an intense focused 325nm laser beam in a square raster of points with 40μm spacing and finally re-examined with 488nm excitation. Periodic changes of the intensities of particular optical centres identify photochromic behaviour. The samples studied by this technique were low-nitrogen CVD and HPHT samples and a boron doped HPHT sample. The restoration of photochromically quenched centres by thermal annealing has also been investigated.
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