||We have prepared Fe-indium tin oxide(ITO) films on glass substrates by dc magnetron sputtering deposition. Fe concentration from 1 to 50% were doped into the ITO films by co-sputtering two targets. After annealing from 200 to 700℃, different iron oxide were formed in the film depended on the annealing temperatures and Fe concentrations. ITO films with low concentrations(<20%) of Fe showed the property of the diluted magnetic semiconductor(DMS). ITO films with high concentrations(>30%) of Fe showed the property of the magnetic granular film.|
X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), x-ray photoelectron spectroscopy (XPS/ESCA), physical property measurement system (PPMS) and super- conducting quantum interference device (SQUID) were used to characterize the film properties, such as the crystal structure, surface morphology, chemical and magnetic property.
With Fe concentration less than 20%, the films were paramagnetic and Fe was mostly oxidized into Fe2O3 measure by XPS. From XRD measurements, the films structure was the typical ITO structure after annealing above 200℃. With Fe concentrations 30%, the ITO and iron oxide structure was no longer observed, and the films exhibited complex magnetic behaviors due to the formation of different iron oxide and different sized of cluster in the film. When the concentrations of Fe higher than 40%, the iron oxide diffraction peak was observed and the ITO structure disappeared. According to the analysis of ESCA, the complex iron oxide structure was found. Granular magnetite (Fe3O4) was responsible for the ferromagnetism in the film because a Verwey transition at about 120K was observed. After annealing at high temperature, the magnetization of the film decrease which was attributed to the oxidation of Fe3O4 into Fe2O3. Phase separation of Fe particles from ITO in the film was observed after annealing temperatures above 500℃。
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