Surface zeta potential and diamond seeding on gallium nitride films

TL;DR

This study investigates the zeta potential of gallium nitride surfaces to optimize diamond nanoparticle seeding, enabling direct diamond film growth on GaN without additional seeding layers.

Contribution

It demonstrates a method to seed diamond nanoparticles on GaN using zeta potential measurements, eliminating the need for low thermal conduction seeding layers.

Findings

Zeta potential of GaN faces is negative in pH 5.5-9.

H-terminated diamond seed solution at pH 8 is optimal for seeding.

Fully coalesced diamond films were grown with high seeding density.

Abstract

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.