| Diamond is a polymorph of carbon. It has many superb properties and applications because of its crystal structure which consists four strong {dollar}spsp3{dollar} covalent bonds.; A thermodynamic program has been developed in an attempt to describe plasma enhanced chemical vapor deposition (CVD) diamond processes in the C-H-O system. It can be used to predict the effects of the types of input gases, the ratios among the gases, and the optimum operation conditions in diamond film deposition. Most importantly, it predicts that the substrate temperature can be lowered by adding oxygen into the feed gases for more choices of the substrate materials. The kinetic analysis for dissociation of chemical species verifies that the thermal plasma processes may provide more abundant dominant species than the low temperature processes, such as filament system, for a higher growth rate. The mathematical model for fluid flow and temperature distributions in the reactor indicates that the gas boundary layer is around 3 mm thick on the substrate surface from an impinging jet under the experimental conditions used. The gas flow rates, the reactor geometry, the plasma temperature, and the distance from the injection probe to the substrate take on important roles in diamond deposition. Finally, a growth model is formulated for the understanding of nucleation and growth.; An inductively coupled plasma (ICP) or radio frequency (RF) plasma enhanced chemical vapor deposition (CVD) system was developed and operated for diamond deposition. It offers a pure reaction environment, a large volumetric flame, and a high temperature source for the deposition. Diamond films have been successfully formed from three gas mixtures: Ar-CH{dollar}sb4{dollar}-H{dollar}sb2,{dollar} Ar-C{dollar}rmsb2 Hsb2{dollar}-{dollar}rm Hsb2,{dollar} and Ar-C{dollar}rmsb2 Hsb2{dollar}-{dollar}rm Hsb2{dollar}-{dollar}rm Osb2.{dollar} The characterizations by scanning electron microscopy, laser Raman spectroscopy, x-ray diffraction and x-ray photonelectron spectroscopy showed that polycrystalline diamond films, diamond-like carbon (DLC) films, and amorphous carbon films had been successfully produced on molybdenum and (100) oriented silicon substrates under a variety of operating conditions. It was possible to decrease the substrate temperature to below 800{dollar}spcirc{dollar}C for diamond films in the C-H-O system. The results from comparative experiments were consistent with the computation results and showed that the behavior of the boundary layer is a key for the deposition. The deposition rate of the film was over 10 {dollar}mu{dollar}m/hr over a 20 mm diameter area and the crystal size ranges from 1 to 2 microns. |
