Synergistic effect of oxidation and complexation on the material removal of pure iron at the nanoscale

Abstract

Chemical mechanical polishing (CMP) has been applied to process iron-based materials. However, the material removal mechanism remains elusive. Accordingly, this study aims to elucidate the synergistic effect of oxidation and complexation on the material removal of pure iron from the microscopic perspective. Atomic force microscopy (AFM) was used to simulate CMP. The AFM results show that when rubbing against a SiO2 probe in the solutions containing only H2O2, pure iron has no material removal. In contrast, with glycine and increasing H2O2, the material removal amount first increases and then decreases, similar to the changing trend in CMP. A synergistic effect exists between oxidation by H2O2 and complexation by glycine, significantly improving the material removal. With glycine and a low concentration of H2O2, iron can be oxidized to Fe2+, then complexed and dissolved, promoting corrosion. Consequently, the surface becomes loose and fragile with relatively low mechanical strength. Under the plowing effect of SiO2, the material removal increases. However, with a high concentration of H2O2, iron can be further oxidized to FeOOH, suppressing corrosion. Hence, the surface grows compact and robust, and the material removal decreases. The findings provide mechanistic insight into the corrosive wear of iron in CMP.