Morphology And Magnetic Properties Of Diluted Magnetic Semiconductor 1D Nanostructure Ni_xSn_1-xO_2-δ

In this thesis SnO₂ nanowires,Ni_xSn_1-xO_2-δ nanowires and Ni_xSn_1-xO_2-δ nanobelts were successfully fabricated by chemical vapor deposition (CVD) method. The X-ray diffraction (XRD), selected area electron diffraction (SAED), scanning electron microscopy (SEM), energy dispersive X-ray (EDS), transmission electron microscopy (TEM), Photoluminescence (PL) and vibrating sample magnetometer (VSM) were used to investigate the microstructure, morphology, magnetic properties of SnO₂ and Ni_xSn_1-xO_2-δ nanowires. The main results are as following:1. SnO₂ nanowires have been deposited on the Si wafer by the catalyzer assisted CVD method. The as-grown nanowires are homogeneous in diameter with the diameters varying from 40nm to 150nm. The length of nanowires can reach 20 microns.2. Ni_xSn_1-xO_2-δ nanowires and nanobelts have been also deposited on the Si wafer by the CVD method. The morphology of the ID nanostructure is sensitive to the fabrication conditions. As the Ar flux rate decreases from 50 sccm to 40 sccm, the 1D nanostructures change from nanowires to nanobelts.3. The growth mechanism of the nanowires and nanobelts have been suggested to be dominated by gas-liquid-solid (VLS) process..4. All of the Ni_xSn_1-xO_2-δ 1D nanostructures exhibit room temperature ferromagnetism (RTFM). With the increasing x, magnetic moment per Ni ion increases at first, reaches a maximum of 3.33μ_B in x = 0.025, then decreases.5. XRD study shows that no peak of Ni clusters are found in the instrument's sensitivity in the Ni_xSn_1-xO_2-δ nanowires samples. It is believed that RTFM does not come from Ni clusters, but is the intrinsic property of the nanowires.6. The experimental studies of the annealing in vacuum and oxidizing atmosphere reveal that oxygen vacancies play a crucial role in introducing ferromagnetism, which implies that the origin of RTFM can be understood by the bound magnetic polaron model (BMP).