Role of Co Clusters and Oxygen Vacancies in the Magnetic and Transport Properties of Co-Doped In2O3 Films

Abstract

The (In1–xCox)2O3 films with x = (0.055, 0.08, 0.10, 0.15) have been prepared by a radio frequency magnetron sputtering technique and investigated by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption fine structure, Hall effect, and room-temperature magnetic measurements. The detailed structural analyses and full multiple-scattering ab initio calculations indicate that most Co2+ ions substitute for In3+ sites of In2O3 lattice and form CoIn2+ + VO complexes with the O vacancy in the nearest coordination shell, whereas a portion of the Co atoms form the precipitate of Co metal clusters for all the (In1–xCox)2O3 films. Despite the formation of Co clusters, magnetic characterizations show that the saturated magnetization Ms of films first increases and then decreases with the increase of Co concentration, suggesting that the small Co clusters are superparamagnetic. The electronic conducting mechanism is dominated by Mott variable range hopping behavior for all the films. The strong localiz...