Synthesis of single crystal diamond by microwave plasma assisted chemical vapor deposition with in situ low-coherence interferometric control of growth rate

• Growth rate of single crystal diamond is measured with a low-coherence interferometry (LCI) in course of MPCVD.
• This in situ interferometric technique allows quick collection of the growth kinetics data in a single growth process run.
• Growth rates above 30 μm/h is achieved in CH4–H2 gas mixtures without adding nitrogen.
• The diamond etching rate in pure hydrogen plasma is measured with LCI.

We performed synthesis of single crystal (SC) diamond by microwave plasma chemical vapor deposition in methane-enriched H2–CH4 gas mixtures, and achieved growth rates more than 30 μm/h, without adding nitrogen in reaction mixture. A low-coherence interferometry (LCI) was employed for precise measurements of the thickness and growth rate of the epitaxial diamond layers in the course of the process. The performance of this in situ technique is demonstrated by continuously monitoring the SC diamond thickness in a single growth run upon variation of CH4 percentage in steps, up to 17%, without switching off the plasma, to produce a “multilayer” diamond film. In addition, etching rate of diamond in pure hydrogen plasma has been evaluated with the same method. The LCI technique allows quick collection of growth kinetics data upon systematic variation of a selected process parameter for the growth optimization.

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