Table 2 Analysis of samples after the process of sputtering the surface with Ar⁺ ions, based on high-resolution XPS spectra.

853.6–853.8

Ni–O (NiO)

1.22

2.45

0.92

854.6–855.6

Ni–O (Ni_xO_y)

0.24

0.43

0.39

707.3–707.9

Fe–O (Fe₃O₄), Fe–C (Fe₃C)

17.56

12.27

24.24

709.1–709.2

Fe–O (FeO)

12.32

11.69

11.73

710.6–711.3

Fe–O (Fe₂O₃)

5.49

5.20

6.06

574.5–575.2

Cr–N (CrN)

4.39

–

8.04

576.0–576.6

Cr–O (Cr₂O₃)

49.63

45.31

31.49

577.4–577.7

Cr–O (CrPO₄, Cr_xO_y)

–

15.58

17.13

578.6–578.8

Cr–O (CrO₃)

9.15

7.07

–