Auger electron spectroscopy (AES, Jeol JAMP-9500F, Wageningen,
The Netherlands) was used to determine the chemicalelements present in the sample at an electron beam energy of
10 keV. In order to perform Auger Electron Spectroscopy analyses
the washed sample was put on a silicon nitride wafer and dried
under vacuum. No sputter coating was applied to the sample.