STUDY OF CUOY LAYERS ON SI AND MGO BY A COMBINATION OF ION-BEAM ANALYSIS (RBS/NRA), X-RAY PHOTOEMISSION SPECTROSCOPY (XPS) AND X-RAY ABSORPTION-SPECTROSCOPY (XAS)

In this work, we examine the possibility of using core-level spectroscopies, X-ray photoabsorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) to obtain a (semi)quantitative measurement of the distribution of copper oxidation states in copper oxide layers of overall stoichiometry CuO(y), otherwise precisely determined by ion beam analysis (IBA), a technique independent of the chemistry. It turns out that the agreement between the analysis of XAS spectra and IBA measurements is excellent as long as y > 0.5, that is for mixtures of CuO and Cu2O. The limits of the applicability of XPS are also discussed. In the field of material sciences, the application of XAS (and also of XPS, to some extent) to determine the Cu(II)/Cu(I) ratios is thus promising in those cases which do not allow precise stoichiometry measurements by ion beam techniques.