Process and apparatus for chemical vapor deposition of diamond films using water-based plasma discharges
A chemical vapor deposition (CVD) process and apparatus for the growth of diamond films using vapor mixtures of selected compounds having desired moieties, specifically precursors that provide carbon and etchant species that remove graphite. The process involves two steps. In the first step, feedstock gas enters a conversion zone. In the second step, by-products from the conversion zone proceed to an atomization zone where diamond is produced. In a preferred embodiment a feedstock gas phase mixture including at least 20% water which provides the etchant species is reacted with an alcohol which provides the requisite carbon precursor at low temperature (55.degree.-1100.degree. C.) and low pressure (0.1 to 100 Torr), preferably in the presence of an organic acid (acetic acid) which contributes etchant species reactant. In the reaction process, the feedstock gas mixture is converted to H.sub.2, CO, C.sub.2 H.sub.2, no O.sub.2, with some residual water. Oxygen formerly on the water is transferred to CO. Hence, an etchant species (H.sub.2 O, OH, O) is replaced in the reactor by CO, a growth species and prevents undesirous consumption of diamond (the net-product). In a preferred embodiment, the apparatus assures conversion by preventing gas circumvention of the conversion zone prior to dissociation in the hydrogen atomization zone to produce the necessary atomic hydrogen for diamond growth.