The maximum of the Cr 2p3=2 peak at 577.0 eV shifts to
a lower value of 576.7 eV with increasing sputtering time
(up to 5 min, Fig. 3). The latter value is typical for Cr3C in
Cr2O3 oxide [13–17]. The higher value at 577.0 eV observed
in the spectrum taken on the surface of the oxide layer is
due to the contribution of trivalent Cr3C species, either in
Cr(OH)3 or CrOOH [17].