Growth of diamond from vapor phase and characterization by Raman, scanning electron microscopy, and X-ray photoelectron spectroscopy

Diamond films have been grown on Si substrates using hot filament assisted chemical vapor deposition (HFCVD) at two different flow rate and temperature regimes. For both regimes, films were grown at different relative concentrations of methane in methane/hydrogen mixtures and were characterized by Raman spectroscopy, SEM and X-ray photoelectron spectroscopy (XPS). In general, the Raman spectra show concentration dependent features characteristic of crystalline diamond, diamondlike carbon, and polycrystalline graphite. SEM micrographs show a transition from densely packed crystallites to a ball shaped morphology with increasing methane concentration. The median grain size of the diamond crystallites increases linearly with time. XPS results reveal differences between the diamond sp3 bonding and graphitic sp2 bonding as well as the extent of s-p hybridization as a function of methane concentration.