Improving electrical properties of ZnO thin films by the combination of annealing and plasma treatment
Date Issued
2008
Date
2008
Author(s)
Shie, Tsai-Yuan
Abstract
In this study, we discuss the methods of improving the conductivity of ZnO thin films. First, we fabricate ZnO thin films and ZnO nanorods by using the sol-gel technique and the hydrothermal method separately. Then we investigate the effects of annealing, doping and plasma treatment on the properties of ZnO thin films. Through the experiments, we find that the ZnO thin film can obtain its best conductivity when annealed at around 600˚C. Also, if we post-anneal them in nitrogen, we can improve the electrical properties of ZnO thin films. We compare the effects of Argon and Oxygen plasma treatment on post-annealed ZnO thin films. The resistivity of the ZnO thin films reduce greatly to the value of 3.15×10-1Ωcm and 6.7×10-3Ωcm by Oxygen plasma treatment and Argon plasma treatment. Photoluminescence spectral features with enhanced ultraviolet emission reveal that oxygen ions may diffuse into the oxygen vacancies of ZnO thin film. However, Energy dispersive spectroscopy (EDS) observation shows that there is no Argon atom in the ZnO film after Argon plasma treatment. Because of the non-reactive properties of inert gases, Argon atom may not diffuse into oxygen vacancies and deactivate the dangling bonds associated with the structure defects. We discuss the possible mechanisms for the decrease of resistivity by plasma treatment on the base of the investigations above. Also, we investigate the combination of annealing, doping and plasma treatment to increase the conductivity of ZnO thin films. We discover that the process of doping aluminum to ZnO cannot be combined with Argon plasma treatment effectively. At last, we transform ZnO nanorods into highly conductive ZnO thin film by annealing and plasma treatment. The ZnO thin films produced in this way posses a resistivity of about 2.3×10-2Ωcm and very clear preferred (002) orientation.
Subjects
ZnO
plasma treatment
annealing
conductivity
Type
thesis
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