Diamond nucleation and adhesion on sintered nitride ceramics

AlN, Si3N4 and SiAlON ceramic materials were sintered from sub-micrometre
powders, by a hot pressing (HP) or pressureless sintering (PLS)
procedures, at temperatures in the range of 1700-1850 degreesC. On these
substrates, diamond coatings of different thickness were grown from a
CH4/H-2 gas mixture, using a HF-CVD apparatus at 30 torr, 750 degreesC.
Different pre-treatments of substrates, including chemical etching,
diamond polishing and carbon seeding by pulsed laser deposition (PLD) of a
graphite target, were used to study and enhance the first stages of
diamond nucleation and growth. The structure and morphology of nitride
ceramic substrates and diamond deposits have been characterised by X-ray
diffraction (XRD) and scanning electron microscopy (SEM). Diamond film
quality and residual stress have been studied by Raman spectroscopy. The
polycrystalline film adhesion on the various pre-treated ceramic nitride
substrates has been evaluated by the indentation technique (Vickers'
indenter). Morphological and structural configuration of polycrystalline
diamond/ sintered ceramic nitride interfaces have been studied by SEM
cross-sections.