A series of diamond films have been grown, all atTsub=1110 K and atomic H concentrations [H]=3×10−10mol/cm3. The acetylene and methyl radical concentrations at the substrate surface were varied independently by factors of up to 4 and 10, respectively, by adjusting the pressure and the input methane concentration, and the effects of these variations on the Raman spectra were examined. The linewidth of the 1332 cm−1diamond feature, thesp2nondiamond carbon feature, and the luminescence yields all increased with increased [CH3]sub, but varying the [C2H2] had no observable impact. A quantitative relationship is provided between thesp2content and [CH3]sub. The luminescence peak, which is the most sensitive feature to [CH3]sub, is due to an impurity from the filament. Using micro‐Raman spectroscopy, large variations are found in the Raman spectra of adjacent crystals and within a single crystal. We attribute these fluctuations to inhomogeneous and anisotropic strains. ©1996 American Institute of Physics.