Electron energy loss spectroscopy for quantitative analysis of the local atomic structure of superthin oxide films on the surface of 3d-metals

In this paper we present a theoretical description of the extended energy loss fine structure (EELFS) formation, and derive simple analytical formulas for the EELFS spectra calculation. Methods of calculating the amplitude and intensity of electron transitions of different multipolarity on excitation of an atomic core level by an electron impact are proposed, and the corresponding test calculations are carried out. The M2,3 EELFS spectra of pure 3d-metals (Fe, Ni, Cu) and stoichiometric oxide films (Fe2O3, NiO and CuO), as well as the K EELFS spectra of oxygen, obtained with a JEOL JAMP-10 Scanning Auger microprobe are presented. A technique of extracting the normalized oscillating parts from experimental EELFS data, based on the use of the calculated electron transition intensities is suggested. The atomic pair correlation functions of the investigated objects are obtained from the experimental EELFS data with allowance for multipolarity of the processes of excitation of the atomic core level by electron impact. The experimental results agree well with the known crystallographic data (partial interatomic distances, coordination numbers and Debye-Waller factors).