DIAMOND FILM QUALITY - EFFECTS OF GAS-PHASE CONCENTRATIONS ON THE RAMAN-SPECTRA

A series of diamond films have been grown, all at T-sub=1110 K and ato mic H concentrations [H]=3x10(-10) mol/cm(3). The acetylene and methyl radical concentrations at the substrate surface were varied independe ntly by factors of up to 4 and 10, respectively, by adjusting the pres sure and the input methane concentration, and the effects of these var iations on the Raman spectra were examined. The linewidth of the 1332 cm(-1) diamond feature, the sp(2) nondiamond carbon feature, and the l uminescence yields all increased with increased [CH3](sub), but varyin g the [C2H2] had no observable impact. A quantitative relationship is provided between the sp(2) content and [CH3](sub). The luminescence pe ak, which is the most sensitive feature to [CH3](sub), is due to an im purity from the filament. Using micro-Raman spectroscopy, large variat ions are found in the Raman spectra of adjacent crystals and within a single crystal. We attribute these fluctuations to inhomogeneous and a nisotropic strains. (C) 1996 American Institute of Physics.