Synthesizing c-axis preferred orientation ZnO:Al transparent conductive thin films by solution way

• Main Authors: Guo-Jhan Gao, 高國展
• Other Authors: Yung-Kuan Tseng
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/35284070857340136715

碩士 === 國立雲林科技大學 === 材料科技研究所 === 97 === In this thesis, it is mainly to synthesize the transparent conductive thin films of Al-doped zinc oxide (Al-doped ZnO, AZO) using a new formula of sol-gel method. We analysis and discuss the formula and the characteristics of its prepared thin films. In this new formula, we use propylene glycol methyl ether (PGME) as an solvent of AZO solution system, zinc acetate as a primary raw material, and add equal mole ratio of monoethanolamine (MEA) as a stabilizer. Then using aluminum nitrate as a doping agent and mixing them all directly, the precursor solution would be completed. Finally, the AZO thin films with high c-axis preferred orientation are deposited on glass substrates by spin-coating with the precursor solution after drying, decarburizing, sintering and annealing thermal treatment. In the study comparing the process parameters of aluminum dopant, sintering temperature and annealing temperature on the impact of AZO thin films, and we explore the optimization of the process parameters for the new formula. The crystalline of AZO thin films are identified by thin-film X-ray diffraction (XRD). The surface morphology and cross-section of the thin films are observed by field emission scanning electron microscope (FE-SEM). Also, optical properties of the thin films are measured by the UV-visible spectrometer, and electronic properties are measured by four-point probe and Hall effect measurement system. From the experimental results of the analysis, we know that AZO thin films deposited on glass substrates with using the precursor solution of PGME solvent are homogeneous. Moreover, we find the microstructure of the thin films with 1.5at% Al doping which is sintered at 550�aC in N2 atmosphere are dense, thick, and c-axis preferred. The transmittance of the thin films are over than 90%. If the films are successively annealed at 500�aC with 95N2/5H2 forming gas, the resistivity could be low to 3.474�e10-3 ���泌m. Moreover, we try to change the reagent of the precursor solution and compared the characteristics of the thin film. If we replace the aluminum nitrate with aluminum chloride as a dopant, the crystalline of the thin films is not affected. The transmittance of the thin films increases to 95%, but the resistivity is up to 7.927�e10-3 ���泌m. We also test to use ethylenediamine as a stabilizer instead of monoethanolamine. The results showed that the preferred orientation of thin films significantly enhanced, but the transmittance fall to 89% and the resistivity become to 1.231�e10-2 ���泌m. Summary, it is found that AZO film with the new formula using PGME solvent not only have high c-axis preferred orientation, but also show excellent optical and electronic property. PGME solvent is safe and easy to deploy the precursor solution, so it can substitute for EGME solvent (acute toxicity) as a new formula for AZO thin-film.