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Epitaxial(0001)-oriented Zn1-xCoxO(x=0.01,0.05 and 0.1) thin films were grown on c-sapphire substrates by pulsed laser deposition.The XRD analysis,optical transmittance and XPS measurements revealed that the Co2+substituted Zn2+ions were incorporated into the lattice of ZnO in Zn1-xCoxO thin films.The electrical properties measurements revealed that the Co concentration had a nonmonotonic influence on the electrical properties of the Zn1-xCoxO thin films due to the defects resulted from imperfections induced by Co substitution.The resistivity remarkably increased and the carrier concentration remarkably decreased in Zn1-xCoxO thin films after oxygen annealing at 600 ℃ under 15 PaO2 pressure for 60 mins.Room-temperature ferromagnetic was observed and the ferromagnetic Co amount was smaller than the nominal Co concentration for Zn1-xCoxO samples before oxygen annealing.After oxygen annealing,the Zn1-xCoxO thin films exhibited paramagnetic behavior.It is suggested that the room-temperature ferromagnetic of Zn1-xCoxO thin films may attribute to defects or carriers induced mechanism.
Epitaxial (0001) -oriented Zn1-xCoxO (x = 0.01,0.05 and 0.1) thin films were grown on c-sapphire substrates by pulsed laser deposition. XRD analysis, optical transmittance and XPS measurements that the Co2 + substituted Zn2 + ions were incorporated into the lattice of ZnO in Zn1-xCoxO thin films. The electrical properties measurements that that Co concentration had a nonmonotonic influence on the electrical properties of the Zn1-xCoxO thin films due to the defects were caused by imperfections induced by Co substitution. The resistivity remarkably decreased and the carrier concentration remarkably decreased in Zn1-xCoxO thin films after oxygen annealing at 600 ° C. under 15 PaO2 pressure for 60 mins. Room-temperature ferromagnetic was observed and the ferromagnetic Co amount was smaller than the nominal Co concentration for Zn1 -xCoxO samples before oxygen annealing. After oxygen annealing, the Zn1-xCoxO thin films exhibited paramagnetic behavior. It is suggested that the room-temperat ure ferromagnetic of Zn1-xCoxO thin films may attribute to defects or carriers induced mechanism.