Cathodoluminescence imaging of nano-indentations in crystals, made using a Berkovich diamond triangular pyramid, was carried out at wavelengths ranging from 380 to 800nm by using a scanning electron microscope. It was shown that the centers of nano-indentations, with estimated residual depths ranging from about 570 to 325nm, luminesced quite strongly and that the spatial resolution of the image appeared to be better than 1µ; as revealed by the structure within the cathodoluminescence image. The centers of larger indents, with residual depths greater than about 1300nm, did not exhibit luminescence. It was suggested that most of the cathodoluminescence which arose from the indentation centers was due to F and F+ colour centers which were produced by plastic flow; with emission peaks at 525 and 375nm. It was also suggested that the relative number density of F+ centers increased with increasing plastic strain; which, in turn, increased with increasing indentation size. Therefore, beyond some critical indentation size, most of the cathodoluminescence from the indentation center was due to the F+ centers. And since this luminescence was beyond the detection sensitivity of the cathodoluminescence system, the indentation center exhibited an absence of cathodoluminescence.

M.M.Chaudhri: Philosophical Magazine Letters, 1998, 77[1], 7-16