Microphotoluminescence and Raman scattering study of defect formation in diamond films

Photoluminescence and Raman spectroscopy are employed to explore the time evolution of defect formation in chemical vapor deposition diamond films for stages of growth spanning nucleation to continuous film formation. Our research is concentrated on three types of defects which give rise to the 1.68 eV optical band, the sp² phase which centers at 1500 cm^-1, and the broadband luminescence at 565-800 nm. The investigation of these types of defects suggests the following conclusions. Si atoms are most likely responsible for the creation of the 1.68 eV optical centers which takes place at the initial stages of growth. Plasma interactions with the Si substrate contribute to the 1.68 eV defect formation. The broad luminescence and sp² bonding defects were not present in the isolated nuclei but were significantly present when a continuous film was formed. Two rates of diamond growth were obtained and the changes of the rates were attributed to the lowering degree of freedom available for the growth of the nuclei as well as to the formation of the sp² phase.