Mechanism of the interaction between Al2O3 and SiO2 during the chemical-mechanical polishing of sapphire with silicon dioxide

Chemical-mechanical polishing of sapphire with colloidal silicon dioxide has been studied with X-ray photoelectron spectroscopy. It has been found that aluminum silicate with the composition Al2SiO5 is formed on the polished crystal surface. The silicon-containing layer thickness reaches 20.5 nm. Its value decreases in the sequence of samples with (0001), ((10\(\bar 1\)2), and (11\(\bar 2\)0) and orientations. A mechanism by which Al2O3 reacts with SiO2 has been proposed. It has been revealed that sapphire samples with different crystallographic orientations exhibit an anisotropic rate of material removal. The anisotropy can be explained by a difference in the rate of the formation of intermediate products during chemical interaction between aluminum and silicon oxides on different planes.