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Preparation and the Investigation of Ferromagnetic Properties of ZnO-based Diluted Magnetic Semiconductors

Author: YangLiHua
Tutor: YuWei
School: Hebei University
Course: Optics
Keywords: Diluted magnetic semiconductors Pulsed laser deposition Structural properties Ferromagnetic
CLC: O484.1
Type: Master's thesis
Year: 2008
Downloads: 33
Quote: 0
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Abstract


This article crystalline ZnO films were prepared by pulsed laser deposition (PLD), substrate temperature, oxygen pressure and substrate material impact on the structural properties of ZnO thin films, to optimize the process parameters. On this basis, the preparation of the transition metal Ni, Mn-doped ZnO-based diluted magnetic semiconductor (DMS) thin-film material, and samples to characterize the structure and characteristics of the combined magnetic behavior analysis to investigate the cause of the samples ferromagnetic. Ni doped sample, its structure and optical absorption analysis showed that, of Ni2 ions have been partially replaced the the Zn2 ions into the lattice structure of ZnO. With the increase of the Ni content, the surface morphology of the film becomes more uneven. Ferromagnetic behavior at room temperature occurs in the case of the Ni content is not too high, and as the Ni content increases, the saturation magnetic moment of a single Ni atoms decreased. For the Ni content is 7 at.% Of the film, and does not detect its ferromagnetic signal. Noteworthy that, when the Ni doping content from 1 at.% Increased to 5 at%, the carrier concentration in the film is reduced accordingly, and increased to 7 at.%, The carrier concentration and increased, this result indicates that rely solely on the carrier concentration can not explain the ferromagnetic behavior of the film ZnO: Ni. All these results indicate that all of ZnO: Ni film microstructure with increasing the doping concentration deteriorates on ZnO: Ni thin film in a long-range ferromagnetic order is disadvantageous. Therefore, it can be concluded that in our sample, the observed ferromagnetic inherent properties of the ZnO: Ni film. These magnetic characteristics of the ZnO: Ni film Synthesis of Ni concentration and the microstructure of the film have a close relationship. For Mn-doped samples, the experimental results show that a suitable concentration of the incorporation of Mn is conducive of ZnO: Mn thin film (002) growth without forming an oxide of Mn, and the same time, all of the films both showed the ferromagnetic properties at room temperature. With Mn content increases, the optical band gap redshift of Mn ions corresponding to the charge transfer absorption transition gradually increased, the saturation magnetization decreases gradually. Raman scattering spectroscopy of the E2 (high) mode films and E2 (low) the scattering characteristic lines and ZnO matrix oxygen atoms and Zn sublattice closely related. With the the Mn incorporation of concentration increased peak width narrowing of Raman spectroscopy E2 (high) mode that the reduction in the number of films in oxygen vacancies. The redshift trend E2 (low) mode showed films donor-type defect zinc interstitial concentration increased, the reduction in zinc vacancy concentration by the main type defects. Shows a ferromagnetic film can be attributed to the nature of defects reflect material structure. Of ZnO: the acceptor-type defects in the resulting ZnO the ferromagnetic Mn film weakening with Mn incorporated matrix zinc vacancy reduction closely related.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > Film growth,structure and epitaxy
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