STUDIES OF DIAMOND FILMS CRYSTALS SYNTHESIZED BY OXYACETYLENE COMBUSTION-FLAME TECHNIQUE

High-quality diamond films/crystals were synthesized using the oxyacet ylene combustion flame technique at atmospheric pressure in a narrow a cetylene-rich region. Three nozzle configurations, single-, tilted- an d multi-nozzle, were used to explore possible ways to improve the unif ormity of diamond films and to increase the deposition areas. It was f ound from the systematic investigation that the surface morphology and crystal structure of diamond films are strongly dependent on the proc essing parameters such as the gas mixture ratio, r, of acetylene to ox ygen, substrate temperature, and nozzle configurations. The appearance of two-dimensional spiral steps on (110) diamond surfaces was observe d, which have not previously been reported in the literature. This phe nomenon is explained using the concept of surface reconstruction. The observed layered steps on (100), (110), and (111) diamond planes stron gly suggest that under certain conditions the synthetic diamond crysta ls could grow with a layer mechanism on any major plane, at least in t he case of films made using combustion flames. Experimental results fr om X-ray diffraction and Raman spectroscopy show the presence of compr essive stress along the [100] direction in the diamond films. The film s also have good optical transparency, indicating potential for optica l coating applications. The hardness, growth rate, film uniformity, an d deposition areas of diamond films are discussed. Advantages and limi tations of these th ree flame-torch deposition techniques are also pre sented.