Structural, optical and magnetic properties of Cr doped In2O3 powders and thin films

The (In1-xCrx)(2)O-3 powders as well as thin films of x = 0.03, 0.05 and 0.07 were synthesized using a solid state reaction and an electron beam evaporation technique (on glass substrate), respectively. The influence of Cr doping concentration on structural, optical and magnetic properties of the In2O3 samples was systematically studied. The X-ray diffraction results confirmed that all the Cr doped In2O3 samples exist cubic structure of In2O3 without any secondary phases presence. The chemical composition analyses showed that all the Cr doped In2O3 compounds were nearly stoichiometric. The X-ray photoelectron spectroscopy analysis of the Cr doped In2O3 thin films showed an increase of oxygen vacancies with Cr concentration and the existence of Cr as Cr3+ state in the host In2O3 lattice. A small blue shift in the optical band gap was observed in the powder compounds, when the dopant concentration increased from x = 0.03 to x = 0.07. In thin films, the band gap found to increase from 3.63 to 3.74 eV, with an increase of Cr concentration. The magnetic measurements show that the undoped In2O3 bulk powder sample has the diamagnetic property at room temperature. And a trace of paramagnetism was observed in Cr doped In2O3 powders. However (In1-xCrx)(2)O-3 thin films (x = 0.00, 0.03, 0.05 and 0.07) samples shows soft ferromagnetism. The observed ferromagnetism in thin films are attributed to oxygen vacancies created during film prepared in vacuum conditions. The ferromagnetic exchange interactions are established between metal cations via free electrons trapped in oxygen vacancies (F-centers).