XAFS study of Co, Ni, Cu or Zn doped TiO2 films

C. E. RODRÍGUEZ TORRES; A. F. CABRERA; L. A. ERRICO; F. GOLMAR; S. DUHALDE; M. RENTERÍA; F. H. SÁNCHEZ

Campinas

Congreso; XVII Reunión Anual de Usuarios del LNLS; 2007

LNLS

A variety of semiconducting materials, called diluted magnetic semiconductors (DMS) combine two properties: semiconductivity and magnetism. Many research groups have focused their e®orts on doping TiO2 with transition metals. Much of the work has been concentrated on Co-doped TiO2 ¯lms, in which ferromagnetism at room temperature has been con¯rmed ¯rst for anatase and later also for ru- tile phase ¯lms. On the other hand some authors have reported remarkable room temperature ferromagnetism on pure TiO2, HfO2 and In2O3 oxides ¯lms and also in ¯lms doped with non-magnetic impurities. All the theoretical and experimental results point out the important role of oxygen vacancies on the origin (or presence) of magnetism, then it is crucial to know the local environment of the impurities in the ¯lms. In this work we present an XAFS characterization of the local environment of the M atoms (M=Co, Ni, Cu or Zn) in doped anatase TiO2 thin ¯lms. All these ¯lms present ferromagnetism at room temperature. We did not found evidences of metallic clusters in any case. The oxidation state is +2 and the local oxygen coordination is similar to MO (CoO, NiO, CuO or ZnO) but, with the exception of Cu, the similitude with these oxides is only in the short range.