Growth and Characterization of Diamond Films Fabricated Using Hot Filament Chemical Vapor Deposition.

A Hot-Filament Chemical Vapor Deposition (HFCVD) system was brought into operation and the process parameters were optimized to fabricate diamond films. Diamond films were grown with varying substrate temperatures (825 ^circC-950^circ C) and methane concentrations (0.25%-5%). An investigation of the effect of substrate temperature determined an optimum temperature of 850^circC. The focus of this study was on films grown with varying methane concentrations. All films were characterized using Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electron Paramagnetic Resonance (EPR) was used to study the paramagnetic defects in these films. Increase in methane concentration resulted in an increase of amorphous carbon content and thus degraded the quality of films, as characterized by Raman spectroscopy. This occurs between 2% to 3.5% methane. Below 2% methane a clearly visible 1332 cm^{-1} diamond Raman line is seen and a faceted crystalline microstructure observed. At 3.5% methane and higher no 1332 cm ^{-1} line is observed only non -diamond carbon peaks are detected also the microstructure becomes ball-like and non-crystalline. Further, the growth rate was also found to increase with increased methane concentration reaching a peak at 2% methane. An EPR spectrum with a g-value of 2.0027(2) was observed for all the samples. It was observed that increasing methane concentration resulted in an increase in concentration and linewidth of the g = 2.0027(2) EPR spectrum. It is concluded that components of the EPR spectrum observed do originate from carbon dangling bond related defects associated with non-diamond carbon phases. The concentration of the EPR center was found to increase markedly between 2% and 3.5% methane consistent with the earlier observation of a transition in film properties through this methane concentration range. The EPR spectrum observed from diamond thin films has often exhibited a pair of partially resolved satellite lines. This issue has not been addressed directly in this thesis, in part due to the lack of reproducible trend in the observation/non-observation of this structure with growth conditions. It is concluded that defects with the required local structure for the observation of satellites exist in diamond and non-diamond carbon phases.