Structural, optical and magnetic properties of pulsed laser deposited Co-doped ZnO films

Zn1−xCoxO films with different Co concentrations (with x=0.00, 0.10, 0.15, and 0.30) were grown by pulsed laser deposition (PLD) technique. The structural and optical properties of the films were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and photoluminescence (PL). The magnetic properties were measured by conventional magnetometry using a SQUID and simulated by ab-initio calculations using Korring–Khon–Rostoker (KKR) method combined with coherent potential approximation (CPA). The effect of Co-doping on the GIXRD and Raman peaks positions, shape and intensity is discussed. PL studies demonstrate that Co-doping induces a decrease of the bandgap energy and quenching of the UV emission. They also suggest the presence of Zn interstitials when x≥0.15. The 10% Co-doped ZnO film shows ferromagnetism at 390 K with a spontaneous magnetic moment ≈4×10−5 emu and coercive field ≈0.17 kOe. The origin of ferromagnetism is explained based on the calculations using KKR method.

This study has been partially funded by the Portuguese Foundation for Science and Technology (FCT) under the project PEST-C/FIS/UI607/2011.The authors O. Karzaziand K.C. Sekhar are grateful for financial support through the Erasmus Mundus Programme EU Mare Nostrum(EUMN),Grant agreement n 2011-4050/001-001- EMA2 and the FCT Grants SFRH/BPD/68489/2010 respectively.The authors would also like to thank Engineer José Santos for technical support at Thin Film Laboratory of University of Minho.