Fabrication And Properties Of ZnCuVO And ZnCuCeO Diluted Magnetic Semiconductor

ZnO-based diluted magnetic semiconductors (DMSs) have been attractingmuch attention, due to the important magnetic properties and the possibleapplications in new spintronics based devices. In the DMSs research field, transitionmetal (TM) doped ZnO is the most widely studied systems to realize roomtemperature ferromagnetism according to the theoretical predictions [3]. It has beenfound that ferromagnetism in DMSs can be enhanced by co-doping. In this thesis,CrCu and CrCe co-doped ZnO samples were synthesized by sol-gel method. Thestructure and properties of the samples have been investigated by the X-raydiffraction (XRD), transmission electron microscope (TEM), X-ray photoelectronspectroscopy (XPS), vibrating sample magnetometer (VSM), and UV Ramanmicroscopy-fluorescence spectrometer.Firstly, Zn0.98xCuxV0.02O (x=0,0.01,0.02and0.03) samples were synthesizedby the sol–gel technology. The XRD results showed that all diffraction peakscorresponded to the wurtzite structure of ZnO. PL measurements showed thatZn0.98xCuxV0.02O powders exhibited that the position of the ultraviolet (UV)emission peak of the samples showed an obvious red-shift and the green emissionpeak enhanced significantly with Cu doping in ZnVO nanoparticle. Magneticmeasurements indicated that room temperature ferromagnetism (RTFM) ofZn0.98xCuxV0.02O was an intrinsic property when Cu concentration was less than3at%. The saturation magnetization (Ms) of Zn0.98xCuxV0.02O (x=0,0.01and0.02)increased with the increase of the Cu concentration.Secondly, Zn0.97Cu0.01V0.02O nanoparticles have been successfully prepared bythe sol–gel method and sintered in air at the different temperature. The effects of theannealing temperature on the properties of the obtained samples were studied. TheXRD results showed that the Zn0.97Cu0.01V0.02O nanoparticles was single phase withthe ZnO-like wurtzite structure when the annealing temperature was<700oC. ThePL spectra revealed that as the annealing temperature increased, the intensity of theUV emission increased and the green emission enhanced sig-nificantly. Magnetic measurements indicated that the samples exhibited ferromagnetism at the roomtemperature. The results of XRD, TEM and XPS revealed that there was noferromagnetic-related secondary phase in Zn0.97Cu0.01V0.02O nanoparticles, theferromagnetism of the Zn0.97Cu0.01V0.02O samples was originated from the fact thatthe Cu and V ions doped into the ZnO lattice. In addition, the Ms increased with theenhance-ment of the annealing temperature.Thirdly, Zn0.97Cu0.01V0.02O nanoparticles have been successfully prepared by thesol–gel method and sintered at600oC in argon and air atmosphere, respectively. Theeffects of annealing atmosphere on the properties of the obtained samples werestudied. The XRD result showed that the Zn0.97Cu0.01V0.02O was single phase withthe wurtzite structure of ZnO. The sample annealed in air had much bettercrystallization. PL shows an increase in green emission when annealing in argon.The two Zn0.97Cu0.01V0.02O samples exhibited ferromagnetism at room temperature.The ferromagnetism in this study was itself property of Cu, V co-doped ZnO and notoriginated from the secondary phase.Finally, we prepared ZnO, ZnCeO and ZnCeCuO nanoparticles by the sol–gelmethod and sintered in Ar atmosphere at600oC. The effects of the Cu doped on theproperties of the obtained samples were studied. The XRD results showed that theZnCeO and ZnCeCuO nanoparticles were single phase with the ZnO-like wurtzitestructure. The PL spectra of the samples revealed that the intensity of the UVemission increased and the green emission enhanced after Cu doped into ZnCeOsample. Magnetic measurements indicated that the ZnCeO and ZnCeCuO sampleshave the room temperature ferromagnetism. The Ms increased after Cu doped.This thesis provides the effective preparation conditions to improve theproperties of ZnO-based DMSs. These results of our investigation will play animportant role in prompting the practical application of ZnO in the future.