A Study Of Fabrication,Morphology Structure,Magnetic And Optical Properties For Diluted Magnetic Semiconductors Of ZnO Nanorods

The rapid development of spintronics and its usefulness in the field of electronic devices makes the magnetic semiconductor become a research hotspot. In recent years, many research groups have successfully prepared diluted magnetic semiconductor material with room temperature ferromagnetism (RTFM). However, the origin of the room temperature ferromagnetism has not been totally understood and remains controversial. There are two main viewpoints with regard to the source of ferromagnetic. One view is that the RTFM is caused by the carrier-induced ferromagnetic exchange coupling, such as RKKY (Ruderman-Kittel-Kasuya-Yosida) type exchange. Another view is that the RTFM is related to defects in the sample, the representative theory is the bound magnetic polaron (BMP) model.In this paper, we successfully synthesized ZnO nanorod arrays and radial-grown hexagonal ZnO rods with Ni doping using a simple hydrothermal method and investigated the morphological, structural, magnetic and optical properties of the samples. The main conclusions are as following:1. ZnO nanorod and Ni-doped ZnO nanorod arrays fabricated by hydrothermal methodThe pure ZnO and Ni-doped ZnO nanorod arrays were prepared successfully on the Si substrate. All the nanorods grow vertically to the substrate plane. And the samples have wurtzite structure and good crystallinity. All the nanorods have a diameter 50-120nm, a length of 1μm-3μm.We found that the diameter of nanorods decreases with the reaction time increasing, while the diameter of nanorods increases with the Ni ion concentration increasing.2. ZnO radial-grown nanorod and Ni-doped ZnO radial-grown nanorod fabricated by hydrothermal method(1) All the samples which are prepared by hydrothermal method without substrate are radial-grown hexagonal rods with diameter from 470 to 720nm and length of 4- 6μm. X-ray diffraction shows that the rods have single crystalline wurtzite structure without other impurity phases.(2) The pure ZnO rods and Ni-doped ZnO rods have ferromagnetism at room temperature, and the saturation magnetization deduces with the increasing diameter of rods. These results reveal that the saturation magnetization of the ZnO rods depends on the surface-to-volume ratio of rods rather than the Ni doping concentrations.(3) The investigation of the photoluminescence spectra indicates that the RTFM is related to the vacancies at the surface of the rods. With the oxygen vacancies decreasing, the saturation magnetization decrease; with the oxygen vacancies increasing, the saturation magnetization increase.(4) The annealing in rich oxygen and reducing atmospheres confirms this argument further.