Room‐temperature ferromagnetism of Cu‐doped ZnO films deposited by helicon magnetron sputtering

Wurtzite structure ZnO films doped with 0.5 and 1.7 at% Cu were deposited by helicon magnetron sputtering. The prepared films exhibited room‐temperature (RT) ferromagnetism (FM). Maximum RT saturation magnetization of 2 emu/cm3 (∼0.3μB/Cu) was observed for ZnO film with 1.7 at% Cu. Cu ions were in a bivalent state as identified by X‐ray photoelectron spectroscopy (XPS). In photoluminescence spectra, the green emission peak increased and redshifted due to the incorporation of Cu or defects induced by Cu incorporation. Since Cu and Cu‐related oxides are not RT ferromagnetic, and no trace of ferromagnetic contamination was detected in XPS results, the observed FM is considered to be an intrinsic property of Cu‐doped ZnO films. The FM was thought to originate from defect‐related mechanisms. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)