522-532Freestanding polycrystalline diamond (PCD)
coatings are of immense technological importance. PCD has been grown over
silicon substrates by microwave plasma assisted chemical vapor deposition
(MWPACVD) process. The coatings are grown by suitable optimisation of the
growth parameters of a 915 MHz microwave reactor. Thereafter, 1:1:1 solution of
hydrofluoric acid (HF), nitric acid (HNO3) and acetic acid (CH3COOH)
is used to etch out the silicon wafer from the backside of the coating. Hereby,
freshly generated nucleation surface, could be characterised by scanning
electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy
and stylus
profilometer and could be compared with the growth side. It is found
that both the nucleation side and growth side are of very high quality (full
width at half maxima, i.e., FWHM -1). The growth side is
(111) textured, whereas, the nucleation side is very smooth with embedded detonation-nano-diamond (DND) agglomerates.
These freestanding coatings are successfully laser cut into different
geometrical shapes. They are found to be optically translucent having
high refractive index. Cross-sectional microscopy of the laser cut edge reveals
novel melting features of the CVD grown diamond columns