| Summary: | 碩士 === 國立臺北科技大學 === 化學工程研究所 === 101 === In this study, transparent conductive film is prepared by sol-gel spin-coating method. The crystal structure was analyzed by using XRD. The surface morphology and roughness were observed by scanning electron microscopy and atomic force microscopy. Using the four-point probe to measure the sheet resistivity of films and utilizing the UV/VIS/NIR spectrometer to measure the transmittance of the materials. The experiment was divided into three parts. The target of this research was prepared the films with high transmittance and low resistivity.
First, the zinc oxide thin films were prepared and the effects of heat treatment conditions on the optoelectronic properties were investigated. The X-ray diffraction studies revealed that thin films have high preferential c-axis orientation in the case of pre-heating temperature at 400℃. It was found that the zinc oxide thin films could achieve the minimum sheet resistivity value of 0.382kΩ/□ after the preheating, post-heating, sintering and annealing process worked at 400℃, 500℃, 500℃,450℃ respectively. The averaged transmittance in the visible light region (400~700nm) was more than 90% and the value of the optical band gap was 3.27eV.
Second, by doping different amounts of aluminum (0.25at%~2.0at%) to improve the electrical conductivity of zinc oxide thin films. The experiment showed that the average transmittance in the visible light region was 92% and the optical band gap increased from 3.27eV to 3.32eV. The atom ratio of Al to zinc oxide at 0.5% could get the best electrical conduction. The electrical resistivity was as low as 2.24 × 10-3Ω‧cm and the grain size was 19.3nm, which was calculated from Scherrer’s equation.
Last, the effects of film thickness and pH value of solution on the optical and electrical properties of 0.5at% aluminum doped zinc oxide thin films were also discussed. The thickness of thin films was measured by ellipsometer. It was found that the average thickness of one layer is about 25nm. It had the electrical resistivity stably when the thickness of thin films deposited over 250nm. The resistivity was 3.57×10-3 Ω‧cm. According to the experimental results, the solution was adjusted to pH 6.63 by adding hydrochloric acid could have the best optoelectronic properties. The resistivity was about 2.94×10-3Ω‧cm and the average transmittance in the visible light region was more than 95%.
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