Photo- and cathodo-luminescence of needle-like single crystal diamonds

Comparative study of photoluminescence (PL) and cathodoluminescence (CL) is performed for the needle-like diamond crystallites. These individual diamond crystallites were obtained by selective oxidation of polycrystalline films produced by plasma enhanced chemical vapor deposition (PE CVD). Two types of diamond films were produced with different composition of gaseous medium. For the first type, gas mixture consisted only of hydrogen and methane during the whole process. And for the second type, nitrogen was injected into the same hydrogen-methane gas mixture during a short time in the middle part of the deposition process. The samples of the needle-like diamonds, produced in these two types of CVD, were studied to determine their PL and CL spectra and spatial distribution of the luminescence intensity at various wavelengths. The characteristics of obtained PL and CL spectra indicate presence of luminescence centers related to nitrogen and silicon impurities in the diamond crystallites. The detected spatial distribution and spectral features of the luminescence are explained by variation of structural perfection at near-surface region of the crystallites.