Cathodoluminescence of defects in diamond films and particles grown by hot-filament chemical-vapor deposition

Point defects, impurities, and defect-impurity complexes in diamond particles and polycrystalline films were investigated by cathodoluminescence (CL) imaging and spectroscopy in a scanning electron microscope. The diamond films and particles were grown by hot-filament methane-hydrogen chemical-vapor deposition at several different temperatures; the nominal deposition temperature ($T_d$) ranged from 600 to 850 °C. Electron-beam energies used to excite the CL were 10–30 keV. By comparing the CL spectra to spectra of known defects in natural and synthetic diamond, the following luminescence centers were identified: (a) 2.156-eV center (zero-phonon line observed at 2.15±0.01 eV) attributed to a nitrogen-vacancy complex; (b) 2.326-eV center (observed peak position at 2.32±0.01 eV), also thought to be a nitrogen-vacancy complex; (c) violet-emitting center (observed peak position at 2.82±0.01 eV), associated with dislocation line defects, whose atomic structure is uncertain; (d) 3.188-eV center (observed peak position at 3.189±0.001 eV), attributed to interstitial nitrogen or a nitrogen–(carbon-interstitial) complex; (e) isolated neutral vacancy (denoted the general radiation center) with principal zero-phonon line at 1.673 eV (observed peak position at 1.675±0.002 eV).