Research On Broad Band Gap High Curie Point Rare Magnetic Semiconductor Material

Diluted magnetic semiconductors (DMS),which show ferromagnetic ordering properties, have attracted much attention for their potential in both basic research and device applications. A key work to realizing devices application is to develop DMS with a high curie temperature.In this thesis, transition metallic elements(TM=Co, Mn, Fe,Ni) doped TiO2 samples were synthesized by a hydrothermal technique, and the preparation process conditions were studied. The crystal structure was characterized using x-ray diffraction and transmission electron microscopy. Magnetic measurements were made in a vibrating sample magnetometer (VSM). Thus the magnetization behaviors and the origin of ferromagnetism of Ti1-xTMxO samples were studied.The preparation process and the magnetic interactions of the Ti1-xCoxO2 samples had been studied firstly. It was showed that a pure anatase phase was indicated for sample TiO2, while mixed phases of anatase and rutile were revealed after doped with Co element, and the concentration of Co element in TiO2 could not exceed 10%. The pure TiO2 did not show any magnetic signals, while the Ti1-xCoxO2(x=0.01-0.04)samples become ferromagnetic. The doping concentration, reaction temperature and reaction time are important factors for sample's ferromagnetism.Based on the study of the Co-doped TiO2 samples, the structure and magnetization behaviors of Ti1-xTMxO2(TM=Mn, Fe, Ni)samples had been experimentally investigated. The samples doped with magnetic elements at low concentration showed ferromagnetic ordering. Similar to Co-doped samples, their concentration also could not exceed 10%, and the samples were in tetragonal morphology and smooth in surface, with a distribution of crystal size in the range of 20-30nm. For the existence of paramagnetic component, the magnetization could not reach to saturation at the magnetic field of 1T. Metal clusters and metal oxides also have been excluded for the origin of the ferromagnetism in samples.In this thesis, the TiO2-based diluted magnetic semiconductors which had a high curie temperature and good reproducibility were prepared by a hydrothermal method.