IN-SITU MASS-SPECTROMETRY DURING DIAMOND CHEMICAL-VAPOR-DEPOSITION USING A LOW-PRESSURE FLAT FLAME

A combination of experiments and detailed kinetic modeling was used to investigate diamond deposition chemistry in low pressure combustion s ynthesis. Microprobe sampling was employed to provide in situ, quantit ative measurements of the stable gas-phase species impinging the growt h surface. The reactant gas ratio was found to be the most critical ex perimental variable. A detailed kinetic model was developed for the st agnation flow system. Comparison of experimental measurements showed v ery good agreement with model predictions. The model was then used to predict the concentration of radical species and analyze the sensitivi ty of predictions to gamma(H), the probability of atomic hydrogen reco mbination on the surface. It was shown that gamma(H) dramatically affe cts the distribution of radical species near the diamond surface. The analysis also indicates that atomic carbon may be an important gas-pha se precursor in this system. Comparison of mole fraction measurements and observations of film morphology were used to draw conclusions on t he growth mechanism.