Local structure study of Co-doped indium oxide and indium-tin oxide thin films using x-ray absorption spectroscopy

Abstract

We have studied the local structural environment of Co in Co-doped indium oxide and indium-tin oxide films, obtained by magnetron sputtering. The Co K-edge x-ray absorption spectroscopic studies have been correlated with the x-ray photoelectron spectroscopy, magnetic, and electrical transport measurements performed on the same films. Different contributions of oxidized (Co2+) and metallic (Co0) cobalt to the observed ferromagnetism in these films are found depending on the host semiconductor and Co content. Homogeneous substitution of Co atoms for the In sites is found in indium-tin oxide films with less than 7at. % of Co, obtained preferably by direct, not sequential, cosputtering. In indium oxide films with similar Co content, obtained by sequential deposition, substitution of Co for the In site is accompanied by a larger static local disorder. As the Co content increases, Co-metal clusters are formed.