chemical preparation of diluted magnetic semiconductors and magnetic properties of the structure

Title: chemical preparation of diluted magnetic semiconductors and magnetic properties of the structure Author: Left Aru Degree-granting units: Lanzhou University Keywords: ZnO;; SnO_2;; Room temperature ferromagnetism;; Bound magnetic polaron Abstract:
Since the discovery of spin-related phenomena and many of its great potential usefulness, spintronics research in the world has been widely carried out. Which is considered the next generation of magnetic semiconductors using electron spin degree Magnetic lifter of freedom the main material manufacturing microelectronic components, have a good prospect.
In recent years, many research groups have prepared a room temperature ferromagnetic diluted magnetic semiconductors, dilute magnetic semiconductors, ferromagnetic origin there is considerable controversy. The theory of magnetic sources are mainly divided into two parts: one is induced by the carrier ferromagnetic exchange coupling, such as the RKKY exchange interaction. Another view of the defects in the sample, representative of the bound polaron (BMP) model.
In this article, we systematically studied the Co-SnO_2 film and powder, Tb-In_2O_3 films and Co-ZnO nanorod arrays of micro-structure, optical properties, electrical and magnetic properties of the main results obtained are as follows:
1. Sol - gel preparation of the Co-SnO_2 powder and film samples
(1) Co-SnO_2 powder and film samples were obtained pure rutile ore structure. And as Co doping increased, the sample grain size decreases, http://www.999magnet.com/products/131-magnetic-lifter   indicating that Co ~ (2 +) doping inhibited the grain growth.
(2) High-resolution electron microscopy showed: the rules and did not sample the lattice distortion or deformation, the selected area electron diffraction (SAED) show that the samples of rutile phase SnO_2, and no impurity phase. X-ray photoelectron spectroscopy studies have shown that the valence state of elements of Co 2 +. The resulting Co ~ (2 +) into the SnO_2 lattice.
(3) has been at room temperature ferromagnetism of Co-SnO_2 powder and film samples, nuclear magnetic resonance (NMR) studies have shown that the magnetic sample is intrinsic to. In the amount of different Co-doped samples, each Co moment with the doping amount increases. Explanation for this phenomenon: the increase in the amount of doping with Co, Co ions decreases the distance between, Co ions by oxygen ions between the antiferromagnetic super-exchange interaction, resulting in the decrease of magnetic moment per Co .
(4) with Sn_ (1-x) Co_xO_2 sol spin-coating on Si (111) and Si (amorphous) films were prepared on the substrate. Studies have shown that, Si (111) substrate is better than the sample crystal Si (amorphous) substrate, while also significantly stronger than the magnetic Si (amorphous) substrates, indicating that closely related to magnetic and crystalline quality .
(5) The chemical resistance of coated samples large magnetic origin can not be carrier-induced exchange interaction model, and models required to explain the BMP. In order to verify whether the BMP model for Co-SnO_2 system, first samples annealed in oxidizing environments, magnetic disappear. The samples were then annealed in a vacuum environment, magnetic and reproduce. The results demonstrate that oxygen vacancies on the Co_xSn_ (1-x) O_2 ferromagnetic system has an important impact, confirmed the BMP model for Co_xSn_ (1-x) O_2 thin film system.
2 sol - gel preparation diluted magnetic semiconductor (In_ (1-xy) Tb_xSn_y) _2O_3 film
(1) different doping (In_ (0.9-x) Tb_xSn_ (0.1)) _2O_3 and (In_ (0.99-y) Tb_ (0.01) Sn_y) _2O_3 film samples were pure cubic structure.
(2) Magnetic studies show that: For a different amount of Tb-doped samples, with the increase in the amount of Tb-doped, Tb magnetic moment of each sample first increased. When the doping amount of 1%, the moment the largest 8.2μ_B/Tb. After the sample moments with Tb doping increases. Electrical studies have shown that: With the increase in the amount of Tb-doped sample the conductivity first increases and then decreases, the magnetic moment of Tb-doped trends and the relationship between the amount of the same, indicating that the magnetic moment of the sample and its conductivity on.
(3) for different amount of Sn-doped samples increase with Sn doping, the sample magnetic moment per Tb first increases and then decreases. Conductivity of the sample doped with Sn and the relationship between the magnetic moment per Tb doped with Sn relationship trend. As the conductivity is proportional to the carrier concentration, indicating that the sample moments and the carrier concentration. Therefore, the system can be the source of the magnetic carrier induced exchange interaction (RKKY) to explain.
3 Hydrothermal diluted magnetic semiconductors Zn_ (1-x) Co_xO nanorods
(1) on Si substrate prepared by the success of the ZnO and Zn_ (1-x) Co_xO nanowire arrays, all of the nanowires are perpendicular to the substrate. As the reaction time and Zn ~ (2 +) ion concentration in solution increases, the diameter and length of the nanorods increases. Nanorods diameter 50 ~ 250nm, a length of 100nm ~ 3μm.
(2) ZnO and Zn_ (1-x) Co_xO have wurtzite structure and have a good optimization approach. Zn_ (0.8) Co_ (0.2) O nanorods with room temperature ferromagnetism.
(3) ZnO, ZnO_ (0.9) Co_ (0.1) O and ZnO_ (0.8) Co_ (0.2) O nanorod emission spectrum at the 391nm band gap shows a strong light, and 613nm show a clear and strong at the red emission peak. Doped, Co-ZnO nanorods red luminescence peak intensity decreased, the gap may be reduced by the doping amount of oxygen due. The peaks rarely reported in the literature. Degree Year: 2009