Self-limiting diamond growth from alternating CFx and H fluxes

Self-limiting deposition (also known as atomic layer epitaxy) of diamond could provide a means for deposition of uniformly-thick films on non-planar substrates at moderate substrate temperatures, with potential applications ranging from cutting tools to microelectronics. We have deposited diamond films on Mo substrates using alternating fluxes of CFx radicals and atomic hydrogen in a quartz-tube hot-filament reactor, observing deposition kinetics that are suggestive of atomic layer epitaxy in certain respects. The CFx radicals, most likely CF3, were generated by reaction of filament-generated atomic hydrogen with an excess of CF4. Under suitable reaction conditions, the growth rate was independent of CF4 duty cycle (CF4/H-2 flow ratio) and equalled roughly one monolayer per cycle, indicating that the surface reached a self-limiting state. However, the growth rate showed a residual temperature dependence and displayed a sublinear dependence on cycle frequency, indicating that the nature of the self-limiting slate (e.g. surface F coverage) is temperature-and time-scale-dependent. Implications of the present results are discussed along with a proposed mechanism. (C) 1998 Elsevier Science S.A.