Tribological Behavior of β-Ga₂O₃ Under Oxidative Aqueous Environment

The performance of gallium oxide (Ga₂O₃) is critically dependent on substrate surface quality, while chemical mechanical polishing (CMP) plays a key role in achieving high-quality finishing of single-crystal Ga₂O₃. However, material removal mechanisms under varying chemical environments remain unclear, thus hampering further optimization. This study investigated the material removal behavior of β-Ga₂O₃ using a tribological approach. Tribochemical interactions between β-Ga₂O₃ and various chemical solutions (deionized water [H₂O], 1% hydrogen peroxide [H₂O₂], and 3% H₂O₂) using different counterbodies (aluminum oxide [Al₂O₃], zirconium dioxide [ZrO₂], and silicon nitride [Si₃N₄]) were systematically analyzed. The results demonstrated a pronounced dependence of tribological behavior on the oxidative aqueous environment. Combined with surface morphology and chemical component analysis, H₂O₂ induced anisotropic selective etching and enhanced surface hydroxylation, leading to an elevated coefficient of friction and wear rate (increasing from ~ 9.74 × 10^-8 mm³/(N·m) in water to ~ 2.27 × 10⁻⁶ mm³/(N·m) in 3% H₂O₂). Furthermore, the tribological performance was governed by the counterbody material. Whereas amphoteric ZrO₂ exhibited mild wear behavior similar to that of Al₂O₃, Si₃N₄ triggered severe mechanical interactions, resulting in the highest wear rate (~ 5.28 × 10⁻⁶ mm³/(N·m)). Cross-sectional microstructural characterization revealed that this interaction leads to the formation of a distinct structural damage gradient in the subsurface. This study provides fundamental insights into the tribochemistry of β-Ga₂O₃, and these findings are anticipated to offer valuable guidance for the future optimization of CMP processes.