Synthesis And Property Of ZnO-based Diluted Magnetic Semiconductors Micromaterials

As a new functional material, Diluted Magnetic semiconductor(DMSs) can combine electronic charge degrees of freedom and spindegrees of freedom, with excellent magnetic, electric, electronic andmagnetic properties, which show a very broad application in spintronicsand optoelectronics. As a semiconductor with broad band gap and highexciton binding energy (60meV), ZnO has a lot of advantages such aschemical stability, rich raw materials, cheap and easy to be doped. ZnOcan be used to prepare diluted magnetic semiconductor with high Tcaccording to theory calculations. So, ZnO become a hotspot of dilutedmagnetic semiconductor materials. The main purpose of our study is toprepare ZnO-based DMSs with excellent magnetic property.In this thesis, we synthesized ZnO-based diluted magneticsemiconductors by low-temperature solution method, and study the effectof the kinds of doped ions and their concentrations on the magneticproperty. The main contents are following:1. The Zn5(CO3)2(OH)6:Fe and ZnCO3:Fe mixture precursors weresuccessfully synthesized by solution method using ZnCl2, FeCl3and(NH4)2CO3as raw materials, and further calcined at high temperature toobtain porous ZnO:Fe DMSs. XRD and SEM showed that the productsare ZnO porous nanoplates with wurtzite structure. EDS and XPS dataindicate that the Fe3+ion replace Zn2+in the ZnO cystal phase. The ZnObandgap (Eg) decrease gradually with the doped ion concentrationsincrease. Room temperature fluorescence spectra show that the doped ionFe3+has obvious effect on the fluorescence strength. The higher thedoped concentrations are, the weaker the fluorescence strength is. This isdue to the formation of the doped energy levels, which influences orreduces the concentration of defects in the ZnO crystals. Gas sensingexperiments indicate that the appropriate Fe3+doped concentration isfavorable to enhance gas sensing effects of acetone and isopropyl alcohol, but excessive doped concentrations will weaken the gas sensing results.Magnetic properties show that Fe3+doped ZnO DMSs have goodroom-temperature ferromagnetism, Curie temperature is350K. And Fe3+doped concentrations have a great influence on the magnetic property,with the Fe3+doped concentration increase, saturated magnetization ofZnO DMSs markedly enhances. In addition, magnetic studies have alsofound that ZnO semiconductor also has ferromagnetism at roomtemperature. We find that the saturated magnetization of Au/ZnO:Fedecreases comparing with ZnO:Fe DMSs.2. The Zn5(CO3)2(OH)6:Mn and ZnCO3:Mn mixture precursors weresuccessfully synthesized by solution method using Zn(CH3CO)2·2H2O,Mn(CH3CO)2·4H2O and (NH4)2CO3as raw materials, and further calcinedat high temperature to obtain porous ZnO:Mn DMSs. We studied theinfluence of the reaction conditions such as the concentration of reactants,kinds of surfactants and solvents on the morphology of products. Theresults reveal that ZnO:Mn are the porous flower-spheres with wurtzitestructure. Mn2+ion replace Zn2+in the ZnO cystal phase.Room temperature fluorescence spectra show that the doped ionMn2+has obvious effect on the fluorescence strength. The higher thedoped concentrations are, the weaker the fluorescence strength is. This isdue to the formation of the doped energy levels, which influences orreduces the concentration of defects in the ZnO crystals. Magneticproperties show that Mn2+doped ZnO DMSs have goodroom-temperature ferromagnetism, Curie temperature is380K. And Mn2+doped concentrations have a great influence on the magnetic property,with the Mn2+doped concentration increase, saturated magnetization ofZnO DMSs markedly enhances. In addition, magnetic studies have alsofound that ZnO semiconductor also has ferromagnetism at roomtemperature. We find that the saturated magnetization of Au/ZnO:Mndecreases comparing with ZnO:Mn DMSs.