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.