**2.2 Chemical characterization**

The chemical composition and state of the surfaces being formed was studied using X-ray photoelectron spectroscopy (XPS). The XPS studies were performed on an Escalab MkII system (England) with Al K radiation (*hν* = 1486.6 eV) and total instrumental resolution of ~ 1 eV. The pressure in the chamber was 10–8 Pa. The binding energy (BE) was referred to the C1s line (of the adventitious carbon) at 285.0 eV. The element concentrations were evaluated from the integrated peak areas after Shirley-type of linear background subtraction using theoretical Scofield`s photoionization cross-sections.
