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

RODRIGUEZ TORRES, C. E. , A.F. CABRERA, ERRICO L.A, GOLMAR F., DUHALDE S., RENTERÍA M., AND SÁNCHEZ F.H.

Campinas, Brasil.

Congreso; XVII Reunión Anual de Usuarios del LNLS (XVII RAU), LNLS, Campinas, Brasil. 12-13 de Febrero de 2007.; 2007

Laboratorio Nacional de Luz Sincrotrón (LNLS)

A variety of semiconducting materials, called diluted magnetic semiconductors (DMS) combine two properties: semiconductivity and magnetism. Many research groups have focused their reports 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 confirmed first for anatase and later also for rutile phase films. On the other hand some authors have reported remarkable roomtemperature ferromagnetism on pure TiO2, HfO2 and In2O3 oxides films and alsoin films doped with non-magnetic impurities. All the theoretical and experimentalresults 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 inthe films.In this work we present an XAFS characterization of the local environment ofthe M atoms (M=Co, Ni, Cu or Zn) in doped anatase TiO2 thin films. All thesefilms present ferromagnetism at room temperature. We did not found evidencesof metallic clusters in any case. The oxidation state is +2 and the local oxygencoordination is similar to MO (CoO, NiO, CuO or ZnO) but, with the exceptionof Cu, the similitude with these oxides is only in the short range.