Growth of diamond films using an enclosed combustion flame
This paper discusses the growth of diamond thin films using an enclosed oxyacetylene torch operating at 700 Torr. Using response surface methodologies, we have systematically explored the parameter space to construct maps of nucleation density, film quality, growth rate, and orientational texture as functions of conditions. The deposition process has been broken down into a nucleation enhancement step and a growth step, and each step is optimized separately. In the study of the nucleation enhancement, we vary the flow ratio=O2/C2H2(R), substrate-flame distance (z), and pretreatment time (t) while holding substrate temperature (Tsub) ≤ 550 °C and flow rate (F)=4 slm. Scanning electron microscopy determines the nucleation density and nucleation uniformity. The best nucleation enhancement occurs at R=0.91, z=50% of the feather length, and t=5 minutes. For the growth study, the variables are R, z, and Tsub(F=4 slm), and we employ two different Raman scattering measurements to assess film quality. In one case, we determine quality using the quality fraction=diamond peak/(diamond peak + nondiamond peak); the second indicator is the luminescence (L) determined from the baseline of the spectrum and is related to defects in the film. The highest quality films appear at high R (0.95-0.97), z=1 mm, and high Tsub(900-1000 °C). We have also determined the growth rate as a function of conditions using infrared spectroscopy and find that the growth rate is a factor of 10 less than in the unenclosed flame (i.e., open to the atmosphere). Films grown for one hour show orientational texturing predominantly in the 〈111〉 direction. © 1995 American Institute of Physics.
Morrison, PW; Somashekhar, A; Glass, JT; Prater, JT
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