Synthesis, Magnetic And Luminant Properties Of ZnO Diluted Magnetic Semiconductors

Based on the research of injection, transportation and manipulation of electron spin, a new subject called"spintronics"emerges in recent years. Due to the possibility of controlling both the spin and charge of electron, spintronics might bring a new revolution in the field of traditional electronics. Meanwhile, as the footstone of designing spin-based devices, diluted magnetic semiconductors have now drawn dramatic attentions.In this dissertation, both Mn- and Ni-doped ZnO nanoparticles have been prepared by an ultrasonic assisted sol-gel method, respectively. Morphologies, structures, magnetism and luminescence properties characterization are performed by using the transmission electron microscope, X-ray diffractometer, Raman scattering measurement system, superconducting quantum interference device magnetometer and cathodoluminescence system, respectively. It is found that the diameters of nanoparticles are about 25 nm. When it is doped with lower contents of Mn or Ni, ZnO keeps a good wurtzite ZnO structure. Raman scattering shows that dopants can result in many defects and lattice disorder in host semiconductors, which causes many new phenomena in Raman scattering, such as the redshift and asymmetric broadening of Raman peaks, the appearance of new Raman peaks etc.With the increment of dopants concentration, the structure of wurtzite ZnO degrades gradually. For the sample doped with 2% Mn, a good hysteresis is observed at 350K, which indicates a good ferromagnetism in the sample. Ferromagnetism with a Curie temperature higher than 300 K has also been observed in Ni-doped ZnO. Ferromagnetism in nanoparticles is discussed in detail in this dissertation, and it is confirmed that the ferromagnetism originates from the intrinsic ZnO doped with Mn or Ni but not from the impurities or the second oxide phases such as MnO and NiO. Meanwhile, it is found that the ferromagnetism strongly depends on the carriers in samples, which indicates that high speed and nonvolatilization devices based on the modulation of ferromagnetism by electric field might come into realization.In the 5th chapter of this dissertation, Mn-doped ZnO films are prepared by a spray chemical vapor deposition method. Morphology, structure, luminescence and magnetism properties are studied in detail. Strong green luminescence can be observed in the samples doped with low Mn contents, and it is found that the intensity of green emission increases with the increment of Mn content, which is different from the results reported by other groups. The physical mechanism of green emission in Mn-doped ZnO films is also discussed.