The role of surface activation prior to seeding on CVD diamond adhesion

A special surface pre-treatment protocol consisting of four steps is proposed to provide high adhesion levels for CVD diamond by hot-filament technique. In step 1, the silicon nitride ceramic substrates are surface ground with 15 µm diamond slurry and mirror-like polished with colloidal silica (0.05 µm). In step 2, plasma etching with CF4 (PE), mechanical anchoring is promoted due to the surface roughness increment. Surface activation (SA) is the following step, where the substrates are subjected to CVD diamond growth conditions for a short time (30 min), leading to the deposition of an amorphous carbon layer responsible for enhancing the nucleation density and the further growth of diamond during early stages of deposition. The final step 4 is 0.5–1 µm diamond powder seeding in an ultrasonic bath.The results show that the Si3N4 ceramic surface modified by the surface pre-treatment protocol allowed a high nucleation density promoting a continuous and homogeneous film of equally sized diamond grains, at a growth rate of ap. 1.5 µm h− 1. Brale tip indentation tests confirmed that highly adherent films are thus produced (no delamination under 900 N).