  Measurement of zeta potential of Ga and N-face gallium nitride has been
carried out as function of pH. Both the faces show negative zeta potential in
the pH range 5.5-9. The Ga face has an isoelectric point at pH 5.5. The N-face
shows higher negative zeta potential due to larger concentration of adsorbed
oxygen. Zeta potential data clearly showed that H-terminated diamond seed
solution at pH 8 will be optimal for the self assembly of a monolayer of
diamond nanoparticles on the GaN surface. Subsequent growth of thin diamond
films on GaN seeded with H-terminated diamond seeds produced fully coalesced
films confirming a seeding density in excess of 10$^{12}$ cm$^{-2}$. This
technique removes the requirement for a low thermal conduction seeding layer
like silicon nitride on GaN.
