Magnetoelectrical properties of W doped ZnO thin films

ZnO thin films were deposited on the Si(100) substrate by rf sputtering using a 99.999% pure commercially bought and a home made target under 100 W power. The home made ZnO target, including 1-2% tungsten, was synthesized via solid state reaction. Thin films were deposited under a flow of 70% argon and 30% O-2 gas mixture followed by post-deposition annealing under 1 Torr oxygen atmosphere. Both deposition and post-deposition annealing were done at 420 +/- 1 degrees C. The structural analyses show that the films were in the [0002] preferred direction and that W atoms are bound to the oxygen atoms by replacing the Zn host atoms. Although no specific change was observed in the magnetic properties as a result of W doping, significant changes in the electrical properties were observed, as determined by the longitudinal and transversal magneto-electrical measurements. It was found that the W impurities induce better insulating properties due to lower carrier concentration and higher resistivity values. On the other hand, the enhanced positive magnetoresistivity and the existence of polarized spin currents, which were not specific for pure ZnO thin films, were observed in W doped ZnO films below 10 K. (C) 2012 Elsevier B.V. All rights reserved.