Experimental confirmation of thermal plasma CVD of diamond with liquid feedstock injection model

A three-dimensional model of diamond chemical vapor deposition in a thermal plasma system has been compared with experimental results to confirm the v alidity of the model in simulating reactor flow patterns and deposit charac teristics. Model and experimental cases were tested with the same boundary and operating conditions. Several sets of operating conditions were analyze d to confirm the validity of the model. Trends in the diamond chemical vapo r deposition system based on the effects of droplet size, injection probe t o substrate offset, the addition of an inert carrier gas, and the differenc es associated with the use of liquid or gaseous precursor feedstock were in vestigated. To test the validity of how patterns predicted by the model, a laser strobe video system was used to map droplet trajectories in the react or. Experimental results were found to support the calculated droplet traje ctories and flowlines in the reactor. Deposition characteristics such as th e mass deposition rate and the area of deposit were examined in the model a nd experimental cases. General trends, with respect to deposition character istics, produced by altering the operating conditions in the experiment, an d respectively the boundary conditions in the model were found to be simila r. Differences between model and experimental results are probably due to t he use of an overly simplified surface chemistry model, which does not take into account graphite deposition. In addition, modeling of radial droplet injection does not take into account non-radial perturbations. (C) 2000 Els evier Science S.A. All rights reserved.