Crystallographic, optical and magnetic properties of Co‐doped ZnO thin films synthesized by sol gel route

Abstract

Abstract ZnO thin films with various Co doping levels (0%, 1%, 3%, 5%, 8%, respectively) have been synthesized by sol gel spin coating method on glass substrates. XRD and XPS studies of the films reveal that cobalt ions are successfully doped into ZnO crystal lattice without changing the hexagonal wurtzite structure. The morphologies are studied by SEM and AFM and show wrinkle network structures with uniform size distribution. With Co doping concentration increasing, the wrinkle network width decreases gradually. The transmittance spectra indicate that Co doping can effectively reduce the optical bandgap of ZnO thin films. Photoluminescence show that all samples have ultraviolet, violet and green emission. When Co doping concentration increases up to 5%, the intensity of violet emission is greatly increased and a strong deep blue emission centered at 439 nm appears. The ferromagnetism of all samples was observed at room temperature. The emission mechanisms and ferromagnetism origination are discussed in detail. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)