Graphitized filament plasma enhanced CVD deposition of nanocrystalline diamond

A novel approach to the deposition of polycrystalline diamond is presented. The technique is based on the hot filament chemical vapour deposition technique (HFCVD). While it is similar to a high plasma power “bias enhanced growth” HFCVD, it relies on a graphite filament rather than on a metal one. It was found that with an appropriate choice of the growth parameters, 4–9% CH4 in H2, filament temperature > 2200 °C, 25 mBar gas pressure, plasma power > 500 W, a long filament lifetime can be achieved, when a simultaneous deposition of graphitic carbon on the hot graphite filament and of nanocrystalline diamond on a substrate facing the filament assembly is realized. In this paper the growth of nanocrystalline diamond films and their characterization (SEM, XRD, AFM) are presented. While the technique is promising for low cost, large area deposition of nanocrystalline diamond films, also the growth of microcrystalline diamond has been observed.

Research Highlights
► The operation of a graphite filament has been stabilized in plasma enhanced hot filament CVD for diamond deposition.
► The method allowed the deposition of diamond with nanocrystalline and microcrystalline morphology.
► Long filament lifetimes (> 30 h) have been achieved for nanodiamond deposition.
► Graphite has a significantly lower cost than Ta and W, is less sensitivity to oxygen pollution and does not lead to metal or metal carbide deposition on the substrate.