Atomic effects in EXAFS structural analysis of mixed Ce oxide thin films

Jana Padežnik Gomilšek,^a Alojz Kodre,^b,c Nataša Bukovec,^d and Irena Kozjek Škofic^d

^a Faculty of Mechanical Engineering, Smetanova 17, SI-2000 Maribor, Slovenia

^b Faculty of Mathematics and Physics, Jadranska 19, SI-1000 Ljubjana, Slovenia

^c Institute Jožef Stefan, Jamova 39, SI-1000 Ljubljana, Slovenia

^d Faculty of Chemistry and Chemical Technology, Aškerčeva 5, SI-1000 Ljubljana, Slovenia

Abstract

Standard structural analysis of cerium compounds by EXAFS (Extended X-Ray Absorption Fine Structure) is unreliable due to particularly strong multielectron photoexcitations (MPE). The collection of the MPE in the pure atomic signal of Ce, to be removed before the procedure, has not been measured or calculated ab initio; our suggestion is to transfer it from another Ce sample. An estimate of MPE contribution is extracted from the absorption spectrum of a Ce compound with known structure by removing the structural signal, calculated ab initio. In a combined fitting procedure of spectra of different compounds, the MPE estimate is refined. Using specific Ce³⁺ and Ce⁴⁺ estimates, absorption spectra of Ce oxide films are prepared free of the major part of MPE signal, especially of its long-wave components, so that a regular EXAFS analysis of the samples is possible.

Key words: EXAFS, Cerium, Electrochemistry