Both oxidizers produce sulfates as reaction byproducts, which are soluble in water, and therefore, they are easily removed with water from the silicon surface without any harmful effects.
Fig. 4 shows the effect on the MRR by the addition of Oxone and K2S2O8 as oxidizers to CeO2 slurry at pH-value 12, where the results with H2O2 have been incorporated in the same figure as reference. It can be seen that for lower oxidizer concentration, the MRR value decreases, regardless the type of oxidizer used. When the oxidizer concentration reaches a critical value of 0.25–0.5%, the material removal rate begins to increase. The observed effects can be explained by the mechanism proposed by Wang et al., [19]: (i) when a small amount of H2O2 is added, a passivation layer is formed on the sample surface which could protect the silicon surface from the OH− present at the basic pH-value 12 value and a smooth surface will be achieved; (ii) nevertheless when H2O2 is added beyond a certain critical value, the passivation layer will be eroded by OH− producing a rough surface, and in consequence there will not be a passivation layer covering the silicon surface.