Raman and photoluminescence investigations of nanograined diamond films

Size-induced transformations in the Raman scattering and photoluminescence spectra of two nanocrystalline diamond materials (an ultrafine explosive powder and the continuous nanograined films) were registered. A narrow peak dominating in the spectrum of 5 nm-size diamond powder appeared to be low-frequency shifted (-11 cm(-1)) and broadened with respect to a single crystal. The peculiarity of the Raman spectra of the nanograined diamond films was a presence of two wide bands at 500 cm(-1) and 1140 cm(-1), corresponding to TA- and TO-like phonons in the spectrum of an amorphous diamond. The photoluminescence spectra of both materials demonstrated a strong temperature independent band with a maximum near 2.2 eV. Increasing the crystallite size led to the weakening of this band simultaneously with the appearance of a well-crystallized diamond peak at 1332 cm(-1) in the Raman spectrum. Measurements were performed at room and liquid nitrogen temperatures.