DEFECT MAPPING OF A SYNTHETIC DIAMOND SINGLE-CRYSTAL BY CATHODOLUMINESCENCE SPECTROSCOPY

Cathodoluminescence (CL) spectroscopy in a scanning electron microscop e was used to identify and to map the spatial distribution of luminesc ent defects in a synthetic diamond single crystal. Several defect CL b ands were observed in the 1.5-3.5 eV region: (i) a band with a zero-ph onon line at 2.156 eV, attributed to a center containing nitrogen and atomic vacancies; (ii) a broadband centered at approximately 2.2 eV, t entatively attributed to a boron-containing center; (iii) a doublet li ne at 2.33 eV, attributed to a nitrogen-containing center; (iv) a zero -phonon line at 2.555 eV, attributed to a nickel-containing center; (v ) a broadband centered at approximately 2.85 eV, attributed to a dislo cation-related center; and (vi) a zero-phonon line at 3.188 eV, attrib uted to a center containing nitrogen and a carbon interstitial. Lines due to free and acceptor-bound excitons were observed in the 5.0-5.4 e V region. The spatial variation of the CL was examined in the vicinity of regions of relatively high dislocation density (approximately 10(6 ) dislocations cm-2), which had been found in a previous x-ray diffrac tion imaging experiment. A quantitative analysis was made of the spati al variation of the band intensities. Upon moving from a relatively de fect-free region to the center of a high dislocation density region, t he intensities of defect bands (i) and (v) increased by very large fac tors (these bands were observed only within the high dislocation densi ty regions); the intensity of defect band (vi) increased by a factor o f approximately 2; the acceptor-bound exciton intensity increased by a factor of approximately 1.3; the intensities of defect bands (ii)-(iv ) decreased by a factor of approximately 2; and the free exciton inten sity decreased by a factor of approximately 7.5.