HFCVD nanostructured diamond films deposited by a combination of seeding suspensions and novel nucleation process

Abstract

The ultrasonic seeding of a substrate with diamond suspensions enriches the surface with nanometre-sized seeds that coalesce and form a closed conformal film during early stages of diamond growth. To get insight on seeds early growth and evaluate the seeding efficiency of different suspensions, silicon samples were exposed to diamond growth conditions before seeding; this leaves a thin carbon film on the substrate surface. Following this step samples were seeded with commercial nanodiamond suspensions, exposed again to growth conditions and characterised by SEM. Results showed that seeding suspensions played a role depending on particle size and nature of dispersing medium. Seeding density was larger and more uniform in samples pre-exposed to diamond growth conditions. The carbon film deposited during the pre-treatment improves deagglomeration of nanodiamond seeds via a more effective interaction between substrate surface and seeds. This procedure represents a viable way to grow thin conformal diamond coatings by HFCVD

Deposition of diamond films on single crystalline silicon carbide substrates

“…The density of voids and grain boundaries at the nucleation surface can be diminished by enhancing the lateral growth of the grains during the initial stages of diamond deposition. This can be achieved by exposing the substrate surface to typical diamond growth conditions for a short period of time, prior to the seeding step (the pre-treatment (PT) described in [33,34]). This procedure (commonly referred to as NNP) enriches the surface with a nm-thick carbon layer that improves the dispersion of the diamond particles during the seeding procedure [34] and induces a lateral growth mode during the early stages of diamond formation, which in turn accelerates grain coalescence and diminishes the number of voids [33].…”

“…This can be achieved by exposing the substrate surface to typical diamond growth conditions for a short period of time, prior to the seeding step (the pre-treatment (PT) described in [33,34]). This procedure (commonly referred to as NNP) enriches the surface with a nm-thick carbon layer that improves the dispersion of the diamond particles during the seeding procedure [34] and induces a lateral growth mode during the early stages of diamond formation, which in turn accelerates grain coalescence and diminishes the number of voids [33]. This was experimentally verified by Sumant et al [35], who studied thoroughly the nucleation surface of nanocrystalline diamond (NCD) films deposited on Si substrates pre-treated and seeded with diamond nanopowders; the roughness of the nucleation surface was as low as 0.3 nm and the sp 2 content was only 1.8%, in comparison with 0.7% on the top side.…”