Fig. 3: Surface analysis of the 3Cr sample using XPS to understand the chemistry and extension of film present on the sample before exposure.

High-resolution X-ray photoelectron spectra: (a, c) Fe 2p and (b, d) Cr 2p spectra obtained from the surface of the polished sample 3Cr; (c, d) XPS depth profile analysis after different levels of ion beam etching. The number N for each level corresponds to different time (N×5 s) of ion beam etching (see subsection 5.3.3).