## 3 Results and Discussion  
Effect of Fenton Reaction on Enhancement in Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) Film Polishing Rate and Corrosion Suppression during CMP  
As a PCRAM-cell material, an as-sputter ternary-chalcogenide film, such as Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film, was laser-annealed at 20 mJ for 10 \(\upmu\)s, which was well crystallized with a face-centeredcubic structure of (200), (220), (222), and (111) dimensions, as shown in Figure S1a. The annealing did not enhance the film density (i.e., \(\sim\)6 g/cm\({}^{3}\)) or the mean film hardness (\(\sim\)3 GPa), as shown in Figure S1b,c. In general, a CMP of chalcogenide film surface (i.e., Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film) is conducted by chemical oxidation on the chalcogenide film surface, followed by mechanical rubbing between abrasives in the CMP slurry and the chalcogenide film surface. Chemical oxidation on the chalcogenide film surface, such as GeO\({}_{2}\), Sb\({}_{2}\)O\({}_{3}\), and TeO\({}_{2}\), requires a CMP slurry with a pH of 1-9, as shown in the Ge, Sb, and Te Pourbaix diagrams in Figure S2. To investigate the degree of chemical oxidation on the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface, the dependence of the chemical oxidation degree on the oxidant (i.e., H\({}_{2}\)O\({}_{2}\)) concentration was examined by dipping a Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film at 70 \({}^{\circ}\)C for 5 min, followed by surface chemical composition analysis by XPS. The 2p 3/2 peaks of Ge and GeO\({}_{2}\) were found at 1217.3 and 1220.2 eV, respectively, as shown in Figure 1a. The 2p 3/2 peak intensity of GeO\({}_{2}\) rapidly increased with a H\({}_{2}\)O\({}_{2}\) concentration of 1-wt% and then slightly increased with increasing H\({}_{2}\)O\({}_{2}\) concentration, while that of Ge decreased abruptly up to a H\({}_{2}\)O\({}_{2}\) concentration of 1-wt% and then decreased slightly with increasing H\({}_{2}\)O\({}_{2}\) concentration, as shown in the inset of Figure 1a. In addition, the 3d 3/2 and 3d 5/2 peak intensities of Sb were located at both 538.1 and 528.1 eV, while those of Sb\({}_{2}\)O\({}_{3}\) were presented at both 539.6 and 530 eV, respectively, as shown in Figure 1b. The 3d 3/2 and 3d 5/2 peak intensities of Sb\({}_{2}\)O\({}_{3}\) at 539.6 and 530 eV considerably increased with the H\({}_{2}\)O\({}_{2}\) concentration and then saturated at a H\({}_{2}\)O\({}_{2}\) concentration of 3-wt%, while the Sb peak intensities slowly decreased until there was a H\({}_{2}\)O\({}_{2}\) concentration of 3-wt%, as shown in the inset of Figure 1b. The peak intensity of Sb 3d 5/2 at 528.1 eV (i.e., 56,454 a.u.) was higher than that of Sb 3d 3/2 at 538.1 eV (i.e., 35261 a.u.). Furthermore, the 3d 3/2 and 3d 5/2 peaks of TeO\({}_{2}\) were discovered at 586.4 and 576 eV, while those of Te were detected at 583.4 and 573 eV, respectively, as shown in Figure 1c. Both 3d 3/2 and 3d 5/2 peak intensities of TeO\({}_{2}\) increased slightly with H\({}_{2}\)O\({}_{2}\) concentration and then saturated at a H\({}_{2}\)O\({}_{2}\) concentration of 2-wt%, while those of Te weakly decreased with increasing H\({}_{2}\)O\({}_{2}\) concentration and then saturated at a H\({}_{2}\)O\({}_{2}\) concentration of 2-wt%. Comparing Figure 1a-c, a higher XPS peak intensity was observed for Sb\({}_{2}\)O\({}_{3}\) (421,875 a.u. ), TeO\({}_{2}\) (160,629 a.u. ), and GeO\({}_{2}\) (158,978 a.u. ), indicating that the chemical oxidation degree of the Ge\({}_{1}\)Sb\({}_{4}\)Te\({}_{5}\) film surface was highly sequenced by Sb, Te, and Ge atoms. Generally, a Ge\({}_{x}\)Se\({}_{y}\)Te\({}_{z}\) film surface CMP slurry uses an oxidizer to enhance the polishing rate, inducing corrosion pits on the Ge\({}_{x}\)Se\({}_{y}\)Te\({}_{z}\) film surface after CMP [22; 23]. To enhance the Ge\({}_{x}\)Se\({}_{y}\)Te\({}_{z}\) film surface polishing rate and to avoid corrosion pits simultaneously, the Fenton reaction between the ferric-ionic catalyst and oxidizer was introduced for a Ge\({}_{x}\)Se\({}_{y}\)Te\({}_{z}\) film surface CMP slurry.