It was recalled that the micro-fracture strength of diamond was governed by the type and density of intrinsic defects in the crystalline structure. Cathodoluminescence methods were used here to evaluate natural diamond which had been thermally plasma-etched. It was found that the etched structure and the cathodoluminescence structure were closely related, and it was clearly demonstrated that the preferentially etched parts were 2.46eV zero-phonon line emission centers at which isolated substitutional N was present.

K.Nishimura, H.Yoshinaga, N.Ikawa, A.Hiraki: Japanese Journal of Applied Physics, 1996, 35[2-3A], L324-7