Formation of diamond films from low pressure radio frequency induction discharges

Diamond films have been deposited in a low pressure, radio frequency (r.f.) induction plasma-assisted chemical vapor deposition system. The r.f.-induction system confines the plasma at the low pressures of operation 0.010–10.00 Torr to permit efficient dissociation of the reactant gases. A variety of chemical systems have been used to deposit diamond, including traditional H 2-CH 4 discharges containing 0.5–2.0% CH 4; H 2-CF 4 discharges containing 4–16% CF 4, and water vapor discharges containing high concentrations of alcohol and/or acetic acid vapors. No molecular hydrogen is admitted to the growth chamber for the water-based processes. The water vapor becomes the functional equivalent of the molecular hydrogen used in more traditional H 2-CH 4 discharges. The success of the low pressure r.f.-induction plasma for diamond growth from the wide variety of chemical systems is predicated on the generation of a high electron density plasma. Parent gaseous molecules are converted into appropriate high temperature stable products such as H, H 2, CO, and C 2H 2 as they traverse the plasma. Quadrupole mass spectroscopy has been used to study the conversion of the water-alcohol vapors to H 2, CO, and C 2H 2 as they pass through the r.f. plasma, 99% of the CH 4O is converted into H 2, H 2O, and C 2H 2. These studies show plasma conversion of H 2O into molecular H 2. The excess oxygen is rapidly converted into CO through interactions of the O, presumably with solid carbon sources. Optical emission from both the water-based discharges and the molecular hydrogen-based discharges shows the propensity for atomic hydrogen generation from these low pressure r.f.-induction discharges.