Correlation between crystalline perfection and film purity for chemically vapor deposited diamond thin films grown on fused quartz substrates

Chemically vapor deposited (CVD) diamond films have been deposited on quartz substrates using a configuration in which the substrate is placed parallel to the direction of the gas flow in the deposition system. Spatially resolved Raman spectroscopy and optical microscopy of the resultant films revealed that (a) as the diamond component of the films increases, the defect density (as measured by the FWHM of the Raman 1332 cm−1 line) decreases, (b) there is a decrease of the quality and perfection of the CVD diamond particles as they overgrow to form a continuous film, and (c) the best quality diamond particles (FWHM) of the 1332 cm−1 line=2.7 cm−1) are produced downstream at the bottom of the plasma ball. It is suggested that the limitations on the continuous film quality appear to be governed not so much by the details of the growth chemistry, but rather by the effects of particle overgrowth.