Friction and wear mechanisms for single crystal GaN based on an electro-Fenton enhanced chemical reaction

Abstract

Electro-Fenton polishing is a chemical mechanical polishing (CMP) technology with enhanced chemical reaction, which hydroxyl radicals (•OH) can be efficiently and controllably generated by using an electric Fenton method. The oxidation and corrosion of single crystal gallium nitride (GaN), and the synergistic mechanism of chemical and mechanical effects in the electro-Fenton polishing process are key to the electro-Fenton polishing of GaN. This article evaluated the effects of different media (electrolyte, H2O2, Fenton, and electro-Fenton) and different conditions (H2O2 mass fraction, means of H2O2 addition, cathode potential, Fe–C catalyst mass fraction, and pH) through ball-disk friction and wear tests. The results showed that electro-Fenton media demonstrated the best oxidation and corrosion effects on the GaN surface among the four media. In the electro-Fenton slurries, the oxidation was very sensitive to the H2O2 mass fraction which showed that 5 wt % H2O2 was the optimal mass fraction; the oxidation efficiency was greatly improved by regularly supplementing H2O2. The friction and wear behavior of GaN exhibited a good response to the cathode potential with the optimal cathode potential being −0.5 V. Meanwhile, the best Fe–C catalyst mass fraction was 3 wt % and the optimal pH was 2. In addition, the friction and wear behavior were investigated, and the energy spectrum tests was carried out to verify the effect of the chemical reaction. The synergistic mechanism of chemical action and mechanical removal in the friction and wear process was revealed. This research provides theoretical support for on-line electro-Fenton polishing technology.