Study On The Preparation And Properties Of Transition Element-Doped ZnO Diluted Magnetic Semiconductor

The term DMS refers to the fact that some fractions of the atoms in a nonmagnetic host such as ZnO, TiO2, SnO2 and InO3, are replaced by transition metal (TM) ions. Among the nonmagnetic matrixes, since ZnO has wide band gap (3.37eV) and large exciton binding energy (60meV), ZnO-based DMSs have been extensively investigated in recent years. Diluted magnetic semiconductors (DMSs), with Curie temperature (Tc) at or above room temperature, have potential application in the spintronic devices such as, magnetic random access memories, optical isolators and quantum computers, etc. Therefore, the study on preparation and properties of transition element-doped ZnO diluted magnetic semiconductor show great significance. In this thesis, transition metal-doped ZnO samples were synthesized by sol-gel and chemical solution deposition method. The structure, magnetic and optical properties of the samples had been investigated in detail by the X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), vibrating sample magnetometer (VSM), superconducting quantum interference device (SQUID) and UV Raman microscopy-fluorescence spectrometer.Firstly, Co-doped ZnO samples were synthesized by sol-gel and chemical solution deopsition method. The experimental results indicated that the samples were ferromagnetic at room temperature and the magnetization decreased with the increase of the sintering temperature for the Co-doped ZnO nanoparticles. Moreover, for the Co-doped ZnO thin films, Co ions could enter the ZnO lattice and Co2+ replace Zn position of ZnO. The samples also were ferromagnetic at room temperature. It was possible to form bound magnetic polarons (BMP) which would be the origin of FM at room temperature in Co-doped ZnO thin films.Secondly, Ni-doped ZnO diluted magnetic semiconductor powder samples were fabricated by sol-gel method. The experimental results showed that Ni-doped ZnO was two valence states and replaced Zn position in ZnO. The samples were ferromagnetism at room temperature. Magnetization of Ni-doped ZnO increased with increasing doping concentration. The ferromagnetism of the Ni-doped ZnO was the nature property though careful analysis. The structure and magnetic properties of Zn1-xNixO obtained in different sintering atmosphere were different due to the numbers of oxygen-related hole in samples. The PL results showed that the lattice of ZnO changed after transition metal Ni entered it, so the UV and the visible emission peak of Zn1-xNixO were varied.Thirdly, the Cr-doped zinc oxide (Zn1-xCrxO,0