Fabrication And Properties Of CrCu And CrCe Co-doped ZnO Diluted Magnetic Semiconductor

The term O-DMSs refers to the fact that some fractions of the atoms in a nonmagnetichost are replaced by transition metal （TM） ions. Among the nonmagnetic matrixes, since ZnOhas wide band gap （3.37eV） and large exciton binding energy （60meV）, ZnO-based DMSshave been extensively investigated in recent years. Since ZnO also has the characteristic ofwavelength photoelectron material, ZnO has been extensively interested. Both experimentalresults and theoretical calculations revealed that different transition metal ions and carrierconcentration in the ZnO based DMSs would strongly influence their properties.Recently, many researchers have tried to dope other ions into the ZnO based DMSs toobtain two metal ions co-doped ZnO in order to change their optical and magnetic propertiesby introducing additional carriers. In this article, CrCu and CrCe co-doped ZnO samples weresynthesized by sol-gel method. The structure, magnetic and optical properties of the sampleshave been investigated in detail.Firstly, the powder was sintered at700oC under argon atmosphere for10hours. PLmeasurements showed that Zn_0.97-xCu_xCr_0.03Opowders and pure ZnO with the Cuconcentration varied from0.00to0.02exhibited obvious blue shift; the green emission peakcould be effectively enhanced with the increase of the Cu concentration. Magneticmeasurements indicated that room-temperature ferromagnetism of Zn_0.97-xCu_xCr_0.03Owas anintrinsic property when Cu concentration was less than0.02. The saturation magnetization ofZn_0.97-xCu_xCr_0.03O（x=0,0.01,0.02） increased with the increase of the Cu concentration.Secondly, Zn_0.95Cu_0.02Cr_0.03O powders have been synthesized by the sol–gel method andsintered in argon atmosphere under different temperature. The PL spectra revealed that theposition of ultraviolet （UV） emission peak of the samples showed blue shift and the greenemission peak enhanced significantly with the annealing temperature increasing from600oCto700oC. Magnetic measurement indicated that room temperature ferromagnetism ofZn_0.95Cu_0.02Cr_0.03O was intrinsic in nature. In addition, the saturation magnetization （Ms）increased with the annealing temperature increased. Zn_0.95Cu_0.02Cr_0.03O samples have beensuccessfully prepared by sol–gel method and sintered in different atmospheres （air and argon）.The results showed that the Zn_0.95Cu_0.02Cr_0.03O samples sintered in different atmospheres hada hexagonal wurtzite structure without any secondary phases. From the photoluminescencespectra, it could be seen that the emission peak of the samples annealed in argon exhibitred-shift. From the magnetic spectra, it could be seen that ferromagnetism was an intrinsic property of the CrCu co-doped ZnO samples. The magnetization （M_S） of Zn_0.95Cu_0.02Cr_0.03Osamples annealed in argon more larger than the magnetization （M_S） of Zn_0.95Cu_0.02Cr_0.03Osamples annealed in air.Finally, CrCe co-doped ZnO DMSs were synthesized by sol-gel method. Theexperimental results showed that Cr ions and Ce ions were at least partially substitutionallyincorporated into the crystal lattice of ZnO. PL measurements revealed that the Ce ionsdoping induced a slight red shift in the UV emission and an increase in the defect emission.All samples showed the obvious hysteresis loops at room temperature. However, With Ceconcentration increasing from0to0.01, the saturation magnetization （Ms） increased.This thesis not only provides the optimized preparation conditions for co-doped ZnOsample, but also obtains some beneficial results in aspects of properties of co-doped ZnOsamples, which will play an important role in prompting the practical application of ZnO inthe future.