Enhancement of magnetic moment of Er-implanted ZnO films by post-annealing in Ar and vacuum

Abstract The Er ions have been introduced into ZnO films prepared by radio-frequency magnetic sputtering (RFMS) on sapphire substrates by ion implantation. The annealing effect on structural and magnetic properties for Er-implanted ZnO films under air, Ar, and vacuum atmospheres at 650 °C have been investigated systematically by a combined characterization of X-ray diffractions, Raman spectroscopy, Photoluminescence, X-ray photoelectron spectroscopy and Superconducting Quantum Interference Device. Strong room-temperature ferromagnetism has been observed for the as-implanted and annealed films. We found that the saturation magnetization varied greatly for different annealing conditions. A considerable enhancement in magnetization is observed for Er-doped ZnO annealed in vacuum, which is accompanied by an enhancement in the concentration of oxygen vacancy. Our results give clear evidence that the enhancement of ferromagnetism is strongly correlated with the increase of oxygen vacancies in Er-doped ZnO.