Effect of oxygen pressure on the structural, optical and magnetic properties of pulsed laser ablated ZnCoO thin films

Abstract: Wurtzite structure ZnCoO thin films with c-axis preferential orientation were synthesized on c-plane sapphire substrates by using pulsed laser deposition (PLD) technique under various oxygen pressures. The structural, optical and magnetic properties of the films were investigated. When the oxygen pressure was relatively low (<1.3Pa), the cobalt was incorporated in the ZnO lattice as Co2+ and substituted for Zn site with no evidence of any impurity phase, whereas inhomogeneous films of wurtzite ZnO phase mixed with cubic CoO phase formed when oxygen pressure was high. The experimental results show that the magnetic behavior is directly related to the presence of intrinsic defects. By changing oxygen pressure to control the amount of Zn vacancies, zinc interstitials and oxygen vacancies, ferromagnetism can be tuned significantly, which is a direct evidence that these defects play an important role in mediating the ferromagnetism in Co-doped ZnO thin films. [Copyright &y& Elsevier]