Evidence of Oxygen Vacancy Mediated Room-Temperature-Ferromagnetism in Co-Doped ZnO Films Upon Hydrogen Treatment

Abstract

The role played by crystallographic defects in the room-temperature ferromagnetism of Co-doped ZnO remains elusive. Here we report the induction of room-temperature ferromagnetism in Co-doped ZnO films upon annealing under a hydrogen atmosphere. High quality Zn1-x Co x O thin films (0⩽x⩽0.1) were grown on Si (100) substrates by pulsed laser deposition. The as-prepared films showed paramagnetic characteristics at room temperature, while after having been annealed at 600°C for 3 h in H2 the films exhibited apparent ferromagnetic behaviors with a room-temperature coercivity value ∼200 Oe. No trace of cobalt containing magnetic phases was found in the samples. The Raman spectroscopy and X-ray absorption near-edge structures results showed an increased oxygen vacancy concentration in the films after the hydrogen heat treatment. These experimental results lead to a conclusion that the observed ferromagnetism is mediated by the oxygen vacancy related F-center.