“…Figure c shows three characteristic peaks at 103.15, 102.6, and 101.85 eV, which should be ascribed to Si 4+ , Si 3+ , and Si 2+ , respectively, indicating the presence of SiO 2 , Si 2 O 3 , and SiO. Figure d shows three characteristic peaks at 532.6, 532.05, and 531.35 eV, which are attributed to O–Si–O, Si–O, and O–Zr–O, respectively.…”