To understand the action of sulfur additions during low-pressure, diamond deposition experiments were carried out in a hot-filament apparatus. As a sulfur compound, H{sub}2S was used and diamond growth was studied for various sulfur additions between 400 and 2200 ppm H{sub}2S/CH{sub}4. To get further information about the interactions of the sulfur compounds during deposition, the deposition parameters substrate temperature and filament temperature were varied. Thermodynamic calculations showed that H{sub}2S reacts with methane to the compound CS during filament activation. At the substrate temperature for diamond deposition (< 1000 ℃) there should be the reverse reaction from CS to H{sub}2S. It could be shown that sulfur reduces the diamond growth rate during the period of nucleation and individual crystal growth. After a diamond layer has been formed, the diamond growth rate increases to values higher than in the undoped system. This can be explained by an additional carbon transport due to the formed CS.
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