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 $\text{Co}\text{ }K$-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 $({\text{Co}}^{2+})$ and metallic $({\text{Co}}^{0})$ 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 $7\text{ }\text{at}\text{.}\text{ }%$ 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.
Highlights
Diluted magnetic semiconductorsDMSthat are ferromagneticFMat room or higher temperatures attract much attention because of their potential applicability in spinbased devices.1 In recent years, high-temperature FM behavior has been reported in a number of transition-metalTMdoped oxides such as ZnO, TiO2, and In2O3.2–4 the origin of ferromagnetism in these systems remains unclear even in most extensively studied ZnO:TM.5 Intrinsic ferromagnetism in TM-doped oxides has been claimed in many papers.6,7 On the other hand, a number of reports point to precipitation of metal clusters or secondary magnetic phases as a likely source of ferromagnetism.8,9 This can be related to the low solubility of TM atoms in host semiconductors.To gain insight into the origin of the magnetic properties of DMS, the determination of the chemical state of the dopant is required
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 oxidizedCo2+͒ and metallicCo0͒ cobalt to the observed ferromagnetism in these films are found depending on the host semiconductor and Co content
Summary
Diluted magnetic semiconductorsDMSthat are ferromagneticFMat room or higher temperatures attract much attention because of their potential applicability in spinbased devices. In recent years, high-temperature FM behavior has been reported in a number of transition-metalTMdoped oxides such as ZnO, TiO2, and In2O3.2–4 the origin of ferromagnetism in these systems remains unclear even in most extensively studied ZnO:TM. Intrinsic ferromagnetism in TM-doped oxides has been claimed in many papers. On the other hand, a number of reports point to precipitation of metal clusters or secondary magnetic phases as a likely source of ferromagnetism. This can be related to the low solubility of TM atoms in host semiconductors. A number of reports point to precipitation of metal clusters or secondary magnetic phases as a likely source of ferromagnetism.. A number of reports point to precipitation of metal clusters or secondary magnetic phases as a likely source of ferromagnetism.8,9 This can be related to the low solubility of TM atoms in host semiconductors. Carefully prepared materials should be analyzed using the adequate techniques to discern whether the dopant is substituted in the host lattice or it is segregated in small aggregates of another chemical specie, such as oxide or metal particles. XANES and EXAFS results at the Co K-edge permit us to discern whether the Co ion is substituted for the In site or it forms aggregates In this way, we may judge whether the observed ferromagnetism in our films is of intrinsic or extrinsic origin
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
