Mechanism of Electrochemically Assisted Friction and Wear Behavior of GaN in KMnO4 Slurry

Electrochemically assisted friction and wear behavior of gallium nitride (GaN) in a KMnO4 slurry was investigated to optimize the composition of the chemical mechanical polishing (CMP) slurry, and the material removal effect of GaN was visually evaluated by using the coefficient of friction (COF) curve and wear area. The results showed that the surface oxidation of GaN was effectively enhanced by KMnO4 and electrochemical assistance. The average COF and wear area of GaN increased with stronger oxidation of the environmental media, which improved the removal of the GaN surface material. Under acidic conditions, the oxidation of KMnO4 for GaN surface was significantly stronger than that under neutral and alkaline conditions, and the GaN surface was effectively oxidized and corroded when the initial mass fraction of KMnO4 was 5 wt%. When the chemical and mechanical actions reached a synergistic effect, the oxide layer generated on the GaN surface was immediately removed by the Si3N4 ball and SiO2 abrasive, which led to a large increase in material removal rate (MMR); the COF curve tended to stabilize, and the average COF increased. The experimental results of the electrochemically assisted CMP of GaN were consistent with the friction and wear test results.