The near-threshold irradiation of B-doped synthetic diamonds was carried out by using a 200kV transmission electron microscope. Both chemical vapor deposited and high-pressure high-temperature synthesized samples were studied. The B-levels were 1017 to 1019cm3. After irradiation, the samples were studied by means of low-temperature (~7K) photoluminescence spectroscopy at various excitation wavelengths. A number of characteristic optical centers were observed within the spectral range of 500 to 800nm. In particular, 2 zero-phonon lines (636 and 666nm) which were formed in B-doped material after near displacement-threshold electron radiation damage were found to be related. The relationship was studied by examining the laser power dependence, at various wavelengths, of their intensities over a wide temperature range. The results were explained in terms of a 3-level model, for a single optical center, that involved a dipole-forbidden excited state of lower energy and a dipole-allowed state of 0.09eV higher energy. A similar behavior was exhibited by a further pair of zero-phonon lines, at 650 and 668nm, which was also formed in the materials. The spatial distribution of centers, and their alteration by ultra-violet excitation, was used to investigate the nature of the 636 and 666nm centers.

Optical Centers Introduced in Boron-Doped Synthetic Diamond by Near-Threshold Electron Irradiation. S.J.Charles, J.W.Steeds, J.E.Butler, D.J.F.Evans: Journal of Applied Physics, 2003, 94[5], 3091-100