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 used to discriminate the Raman signals from the plasma emission. The in situ detection of a diamond film during its growth on a single crystal of alumina substrate is presented. The detectivity of the method has been estimated to be about a few tens of μg/cm² for an acquisition time of 800 s. Peak shifts are interpreted in terms of temperature and stress dependences. It is shown that the diamond in the first stages of deposition is free of stress, then when grains come into contact compressive stresses are observed, when the film thickness reaches about 1 μm stresses are relaxed.