IN-SITU RAMAN-SPECTROSCOPY DURING DIAMOND GROWTH IN A MICROWAVE PLASMA REACTOR

An experimental set-up designed for in situ Raman analysis during the growth of diamond films in a microwave plasma reactor is described. A gated multichannel detection synchronized with a pulsed YAG laser is u sed to discriminate the Raman signals from the plasma emission. The in situ detection of a diamond film during its growth on a single crysta l of alumina substrate is presented. The detectivity of the method has been estimated to be about a few tens of mug/cm2 for an acquisition t ime of 800 s. Peak shifts are interpreted in terms of temperature and stress dependences. It is shown that the diamond in the first stages o f deposition is free of stress, then when grains come into contact com pressive stresses are observed, when the film thickness reaches about 1 mum stresses are relaxed.