Analysis of Nitrogen Defects in Diamond with VUV Photoluminescence

Various diamonds were analyzed with photoluminescence (PL) spectra excited with synchrotron radiation in the wavelength range 160-250 nm. The emission of type IaAB diamond begins near 300 nm and extends to 700 nm; two broad lines with maximums about 419 and 469 nm correspond to energies 2.96 and 2.64 eV, respectively. The spectral features observed in the PL excitation spectra show two vibrational progressions, A and B, related to nitrogen defects in diamond. Progression A has a spacing 1266 ± 20 cm(-1) and is associated with the N2 (or A) center of a nitrogen defect, whereas progression B has a spacing 1177 ± 20 cm(-1) related to the N4 (or B) center of a nitrogen defect. These vibrational progressions in PL excitation spectra of N2 and N4 centers in type IaAB diamond are here identified for the first time. We suggest the use of PL spectra excited in the region 170-240 nm to analyze and to identify the type of diamond.