CORRECTION OF PEAK SHIFT AND CLASSIFICATION OF CHANGE OF X-RAY PHOTOELECTRON-SPECTRA OF OXIDES AS A RESULT OF ION SPUTTERING

Round-robin experiments have been performed to correct binding energy shifts of XPS spectra for oxides by charge-up which results from irradiation of x-rays or ion sputtering and to determine criteria for the change of chemical state resulting from Ar ion sputtering. Al2O3, SiO2, MgO, TiO2 and NiO, in plate and powder form, were used for the experiments. We have revealed that the binding energy difference between the Al 2p (Si 2p or Mg ls) line and the 0 ls line gives a better correction for the measurements of Al2O3 (SiO2 or MgO) than that between the Al 2p (Si 2p and Mg 1s) line and the C ls line. After Ar ion sputtering, TiO2 and NiO are reduced and new components appear in the XPS spectra. For Al2O3 and SiO2, the damage is induced by sputtering and the full width at half-maximum (FWHM) values of XPS spectra increase, while MgO is unchanged. We have shown that the changes of oxides caused by ion sputtering depend on the change of free formation enthalpy and ionicity. We have also shown that both plate and powder samples are useful as standards to determine the binding energy from XPS spectra.