## 3 Results and Discussion
Moreover, the relative XPS peak intensities at 584-eV (i.e., Te of Te3d 3/2) and 573-eV (i.e., Te of Te3d 5/2) binding energies were almost independent of the catalyst PDTA-Fe concentration. This result indicates that the Ge and Sb atoms in the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface are well chemically oxidized rather than the Te atoms with dissolved O\({}_{2}\) and radicals (i.e., HO\({}_{2}\)\({}^{\bullet}\) and OH\({}^{\bullet}\)). Thus, the formation of a chemically oxidized layer on the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface is mainly induced by Sb\({}_{2}\)O\({}_{3}\) and TeO\({}_{2}\) rather than GeO\({}_{2}\), and the chemical oxidation degree of Sb\({}_{2}\)O\({}_{3}\) and TeO\({}_{2}\) was evidently enhanced with the catalyst PDTA-Fe concentration under the Fenton reaction. As a result, the polishing-rate of the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface linearly increased with the catalyst (i.e., PDTA-Fe) concentration, as shown in Figure 2.  
The detailed Fenton reaction between the Fe\({}^{3+}\) catalyst and H\({}_{2}\)O\({}_{2}\) and chemical oxidation (i.e., formation of GeO\({}_{2}\), Sb\({}_{2}\)O\({}_{3}\), and TeO\({}_{2}\)) can be understood by the following equations [26; 27; 28]. \[\mathrm{C}_{11}\mathrm{H}_{14}\mathrm{FeN}_{2}\mathrm{O}_{8}\cdot\mathrm{NH}_ {4}\rightarrow\mathrm{Fe}^{3+}+\mathrm{NH}_{4}^{+}+[\mathrm{C}_{11}\mathrm{H}_{ 14}\mathrm{FeN}_{2}\mathrm{O}_{8}]^{4-} \tag{1}\]  
Figure 3.0  
Figure 3.1  
Figure 3.2  
Figure 3.3  
Figure 3.4  
Figure 3.5  
Figure 3.6  
Figure 3.7  
Figure 3.8Figure 3.9 Figure 3.0 (12) Figure 3.1 (13) Figure 3.2 (14) Figure 3.3 (15) Figure 3.4  
First, PDTA-Fe (i.e., \(\text{C}_{11}\text{H}_{14}\text{Fe}_{2}\text{O}_{8}\text{-NH}_{4}\)) was dissolved with Fe\({}^{3+}\), NH\({}_{4}\)\({}^{+}\), and [\(\text{C}_{11}\text{H}_{14}\text{N}_{2}\text{O}_{8}\)]\({}^{4-}\) at pH 2, as shown in equation (1). The Fenton reaction between the Fe\({}^{3+}\) catalyst and H\({}_{2}\)O\({}_{2}\) generates dissolved O\({}_{2}\) and radicals (i.e., \(\text{HO}_{2}^{\bullet}\), OH\({}^{\bullet}\), and \(\text{O}^{\bullet}\)\({}^{-}\)), as shown in Equations (2)-(7). As a result, chemically oxidized Ge\({}_{5}\)Sb\({}_{4}\)Te\({}_{5}\) film surface (i.e., formation of GeO\({}_{2}\), Sb\({}_{2}\)O\({}_{3}\), and TeO\({}_{2}\)) atoms are produced by the chemical reactions of Ge, Sb, and Te atoms with dissolved O\({}_{2}\) and radicals (i.e., \(\text{HO}_{2}^{\bullet}\) and OH\({}^{\bullet}\)), as shown in Equations (8)-(16). The above equations indicate that the chemical oxidation degree of the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface increases linearly with the catalyst (i.e., PDTA-Fe) concentration. Effect of Corrosion Inhibitor with Protonated Amine Groups on Corrosion Suppression and Corrosion Inhibition Mechanism  
Although the Fenton reaction in a Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP slurry can significantly suppresses CMP-induced corrosion on the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface, as shown in Figure 3, an actual Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP process using a Fenton reaction-based CMP slurry can also result in CMP-induced corrosion, producing a polishing-induced void or a recess at a nanoscale confined-structure PCRAM-cell [22; 23]. Thus, to avoid corrosion at the nanoscale confined-structure PCRAM-cell after Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP, a corrosion inhibitor was mixed with the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface CMP slurry using the Fenton reaction. A corrosion inhibitor with a protonated amine functional group was selected, that is, polyethyleneimine (PEI) with a molecular weight of 25,000 g/mol.