The Influence Of DC Arcjet Plasma’s Properties On Deposited Diamond

The history of chemical vapor deposition (CVD) diamond was reviewed. The "art-of-date" of CVD diamond was also stated for the progresses and the problems. Base on these literatures, a scientific issue, the influence of plasma’s properties on CVD diamond, was definitely proposed.The high power DC arcjet plasma deposition system was used to deposit diamonds, of which included micro-crystalline diamond films, nano-crystalline diamond films and ultranano-crystalline diamond films as well as millimeter-sized diamond grains. By using SEM, TEM, Raman spectra and XRD, the deposited diamonds were studied of their morphologies, compositions and orientations. A new type of morphology,"pineapple-like" morphology, was found, which was a middle-stated morphology transferring from microcrystalline film to nano-crystalline film. These experimental deposition results indicated that the plasma’s properties influenced the deposits very much.Optical emission spectra (OES) was applied to diagnose the plasma in order to find out the space distribution of the radicals in the deposition zone and the change with the deposition time. It was found that the intensity of radical changed little at the distance over5mm above the substrate, otherwise, it changed obviously. On the other hand, the intensity of the radical also would vary with the increase of deposition time. In our system, the intensity would be stable during the time less than30hr, and it would be unstable over30hr.The commercial code, FLUENT, was utilized to stimulate plasma flow field with different experimental parameters. The influence of the velocity of jetted plasma and the distance of the pass through path on the size of stagnation zone and thickness of boundary layer was analyzed.Base on the simulation results, the observation point of "refining" OES was then confirmed. Under this condition, the incubation period of nucleation was studied on the polycrystalline diamond film by high FCH4/FH2.It was found that an amorphous carbon formed first, and then, nucleation occurred. The detected size of nuclei was about2-3nm by HREM. Combining the results of TEM and OES, the incubation period was therefore confirmed during6-8minutes under the condition of FCH4/FH2>15%.Millimeter-sized diamond grains were deposited on (100) surface of the natural Ⅱa diamonds by two modes, movable mode and unmovable mode. In movable mode, the growth rate could be about52μm/h. The higher substrate descending rate would result in ATG type morphology, and then causing the growth of poly-crystallization. In unmovable mode, the growth procedure was almost as same as that of diamond film deposition. In this mode, the holding way of substrate was the key factor to determine the continuous growth.