CATALYTIC EFFECTS ON DIAMOND FILM FORMATION BY PLASMA-ASSISTED CHEMICAL VAPOR-DEPOSITION

Limited control of the microstructure of diamond films has been possible through changes in reactant gases, substrate temperature, and substrate surface preparation. The presence of an operating heterogeneous catalyst during the deposition of the diamond phase could alter either nucleation or growth. In this work, supported palladium catalysts in the form of Pd Al2O3 and Pd/graphite were wiped on a Si(100) substrate prior to deposition. The resulting films were compared with films deposited on the untreated substrate, and previous results on diamond-polished, Al2O3-polished, and graphite-wiped substrates. Nucleation and growth rates were statistically measured in the scanning electron microscope. The catalytically treated substrates were the only cases where nucleation occurred after the first 2 min of deposition. Two distributions of diamond particles appeared on the palladium-treated substrates, one very similar to that appearing on the untreated substrate, and one with much smaller crystallites, which apparently nucleated during the deposition process as the larger crystallites were growing. The diamond particles on the catalytically treated substrates were strongly associated with the palladium particles, again indicating a catalytic effect on nucleation. Scanning electron microscopy-energy-dispersive spectroscopy analyses after deposition revealed palladium, indicating that the catalyst was still operating late in the deposition process. The presence of a catalyst may have produced hydrocarbon fragments which can nucleate the diamond phase at sites different from those consumed in the initial burst of nucleation. © 1992.