Surface zeta potential and diamond growth on gallium oxide single crystal

TL;DR

This study presents a method for growing diamond on gallium oxide single crystals by measuring surface zeta potential, using seed layers, and protecting the substrate with thin oxide layers, resulting in thin diamond films characterized by SEM and Raman.

Contribution

It introduces a novel approach to grow diamond on gallium oxide substrates by surface charge measurement and protective oxide layers, overcoming previous growth challenges.

Findings

Negative zeta potential of gallium oxide at pH ~4.6.

Effective protection of gallium oxide with SiO2 layers during diamond growth.

Diamond layers under 2.8 GPa compressive stress, confirmed by Raman.

Abstract

In this work a strategy to grow diamond on $\beta$-Ga$_2$O$_3$ has been presented. The $\zeta$-potential of the $\beta$-Ga$_2$O$_3$ substrate was measured and it was found to be negative with an isoelectric point at pH $\sim$ 4.6. The substrates were seeded with mono-dispersed diamond solution for growth of diamond. The seeded substrates were etched when exposed to diamond growth plasma and globules of gallium could be seen on the surface. To overcome the problem $\sim$100 nm of SiO$_2$ and Al$_2$O$_3$ were deposited using atomic layer deposition. The nanodiamond seeded SiO$_2$ layer was effective in protecting the $\beta$-Ga$_2$O$_3$ substrate and thin diamond layers could be grown. In contrast Al$_2$O$_3$ layers were damaged when exposed to diamond growth plasma. The thin diamond layers were characterised with scanning electron microscopy and Raman spectroscopy. Raman spectroscopy revealed the diamond layer to be under compressive stress of 1.3 -- 2.8GPa.