  This study focuses on the self-assembly and subsequent diamond growth on
SiO$_2$ buffered lithium niobate (LiNbO$_3$) and lithium tantalate (LiTaO$_3$)
single crystals. The zeta-potential of LNO and LTO single crystal were measured
as a function of pH. They were found to be negative in the pH range 3.5-9.5.
The isoelectric point for LNO was found to be at pH $\sim$ 2.91 and that of LTO
to be at pH $\sim$ 3.20. X-ray photoelectron spectroscopy performed on the
surfaces show presence of oxygen groups which may be responsible for the
negative zeta potential of the crystals. Self-assembly of nanodiamond particles
on LTO and LNO, using nanodiamond colloid, were studied. As expected, high
nanodiamond density was seen when self-assembly was done using a positively
charged nanodiamond particles. Diamond growth was attempted on the nanodiamond
coated substrates but they were found to be unsuitable for direct growth due to
disintegration of substrates in diamond growth conditions.. A $\sim$100nm thick
silicon dioxide layer was deposited on the crystals, followed by nanodiamond
self assembly and diamond growth. Thin diamond films were successfully grown on
both coated crystals. The diamond quality was analysed by Raman spectroscopy
and atomic force microscopy.
