LOCAL GROWTH-STUDIES OF CVD DIAMOND USING A PROBE-LIKE SUBSTRATE

Diamond films produced by Ar/H-2/CH4 RF induction plasmas have high gr owth rates but often lack umiformity across the substrate, in this pap er, the diamond growth on a probe-like molybdenum substrate, 4.76 mm i n diameter, is correlated with the location of the probe in the plasma flame, Optical emission spectroscopy is used to characterize the plas ma during deposition, The differences in gas temperature and electron density between the central and the outer region of the dame, as well as the variations in heat flux to the substrate at the different posit ions, are well reflected in the formed deposit, It is shown that unifo rm growth can only be expected within the homogeneous core of the plas ma, The paper also addresses the gas phase boundary layer above the gr owing film, Spatially resolved emission spectroscopy measurements of c oncentration evolution inside the boundary layer region are made possi ble by the small dimensions of the substrate, A decrease in thermal bo undary layer thickness from approximately 4.5 to 3 mm induced by an in crease in plasma power enhances the lateral growth of the individual d iamond crystallites and improves surface coverage, The typical film th ickness growth rate of 70 mu m/h is, however, not seen to be affected.