GROWTH OF DIAMOND FILMS USING AN ENCLOSED COMBUSTION-FLAME

This paper discusses the growth of diamond thin films using an enclose d oxyacetylene torch operating at 700 Torr. Using response surface met hodologies, we have systematically explored the parameter space to con struct maps of nucleation density, film quality, growth rate, and orie ntational texture as functions of conditions. The deposition process h as been broken down into a nucleation enhancement step and a growth st ep, and each step is optimized separately. In the study of the nucleat ion enhancement, we vary the flow ratio=O-2/C2H2 (R), substrate-flame distance (z), and pretreatment time (t) while holding substrate temper ature (T-sub) less than or equal to 550 degrees C and flow rate (F)=4 slm. Scanning electron microscopy determines the nucleation density an d nucleation uniformity. The best nucleation enhancement occurs at R=0 .91, z=50% of the feather length, and t=5 minutes. For the growth stud y, the variables are R, z, and T-sub (F=4 slm), and we employ two diff erent Raman scattering measurements to assess film quality. In one cas e, we determine quality using the quality fraction=diamond peak/(diamo nd peak + nondiamond peak); the second indicator is the luminescence ( L) determined from the baseline of the spectrum and is related to defe cts in the film. The highest quality films appear at high R (0.95-0.97 ), z=1 mm, and high T-sub (900-1000 degrees C). We have also determine d the growth rate as a function of conditions using infrared spectrosc opy and find that the growth rate is a factor of 10 less than in the u nenclosed flame (i.e., open to the atmosphere). Films grown for one ho ur show orientational texturing predominantly in the [111] direction. (C) 1995 American Institute of Physics.