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The Preparation and Optical Properties of ZnO Thin Films Doped with Mg by Ultrasonic Spray Pyrolysis Method

Author: DongLiNa
Tutor: WangYuXin
School: Liaoning Normal University
Course: Optics
Keywords: ZnO thin films Mg doped Ultrasonic Spray Pyrolysis Method(USP) PLspectrum
CLC: O484.41
Type: Master's thesis
Year: 2012
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Abstract


Zinc oxide(ZnO) and related Zn(Mg, Cd)O material systems have attracted considerable attention as an excellent candidate for the next generation of ultraviolet light emitting and lasing devices. The p-type doping and band gap engineering in semiconductors are two key techniques for fabricating a double heterostructure light emitting device using ZnO active layer. Great progress has been made recently in the p-type doping and p-n junction device based on ZnO material in our group. The applications of ZnO on the UV detector, a luminous tube, a surface acoustic wave device and sensitive pressure sensitive device have become a hotpot for better progress in science, better physical and chemical properties in optics, electric, thermonics, magnetics of ZnO thin films material and the greater potential value. Experiments have proved that the doping is a good method. By choosing appropriate preparation conditions and doping elements, better performance can be obtained.In this thesis, the pure ZnO films and the doped films with different substrate temperatures and concentrations were prepared in quartz glass substrate by the ultrasonic spray pyrolysis technique, the morphology, microstructure and optical properties were analysis systemically. The experimental results show that the optimal condition of pure ZnO films is that the substrate to the nozzle distance is2.5cm; the carrier gas flow rate is0.8L/min. Basing on this condition, ZnMg0.1O thin films were prepared under different temperatures and their transmittance is above80%. Their surface morphology becomes smooth and uniform. The excitation and emission spectra showed that deep level luminescence also decreases gradually with the temperature increasing between450℃and530℃. But when the temperature increases to550℃, the grain increases and bumps. At the same time, crystal quality is debased and light properties are decreased. So the optimal temperature of ZnMg0.1O is530℃. Then the MgxZn1.xO thin films doped with Mg at x=0.05,0.1,0.15,0.2and0.3were investigated by SEM, XRD, PL spectrum and transmission spectrum. The results show that grain size of samples largens with the increasing concentration. The sample at x=0.2is more uniform and smooth. And the crystallization quality is decreased with increasing concentration. When x is0.3,the sample appears polycrystalline phenomenon. When x is lower than0.2,PL spectrum appears blue shift with the increasing Mg content and no obvious deep level luminescence, which illustrates that the films have no obvious impurity and defect with better crystallization quality. But when the concentration reaches0.3, the PL peak moves to long wavelength. Maybe it is due to the more instead of Zn with Mg, which leads to the appearance of polycrystalline. It is also associated with XRD results. The band gaps obtained by transmission spectrum in different concentration are discussed. And they widen with increasing Mg content. The results is lower than the PL band gap value, maybe it is for the hypothesis that transmission spectrum reflectivity is not zero results.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > The nature of the films > Optical Properties
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