| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 94 === In this research, zinc oxide thin films were prepared via the solution chemistry. In addition to investigate the effects of water concentration and electrolytes on the structure, crystallity, microstructure and electro-optical properties of ZnO films, this research also studied the effects of doped Al on enhancing the conductivity and transmittance of zinc oxide films. In the experimental process, the precursors were zinc acetate and alcohol, and two aluminum compounds were used as dopants. It was observed that water concentration and electrolyte could remarkable affect the gelation rate of solution, the gelation rates increased with decreasing of water content but with increasing of acidic electrolyte amount. With different amount of water, electrolyte, and doped Al, the thermal activity and infrared spectra of films did not show significant difference. The doped-ZnO film (with 1at% Al) had a better crystallinity, but the crystallinity of film decreased with increasing the doped amount. The dried films began to form the ZnO crystalline phase after heat-treatment at 200℃.
Increasing the contents of water and electrolyte that would cause the film to form significant agglomeration. On heat-treatment at 400℃, the undoped-ZnO films had average grain size of 25±3nm, while the doped-ZnO films with 2.0at% AlCl3 and 1.0at% Al(NO3)3 had average grain sizes of 19±3nm and 15±3nm, respectively. Both the dried undoped and doped films possessed mesopore structures. Their pore sizes increased with decreasing dopant amount, but increased with firing temperatures.
The visible transmittance of films decreased with increasing the amounts of water and electrolyte. Upon firing at 600℃, the undoped-ZnO films had transmittance of 20% in visible light range, while the doped-ZnO films (with 3.0at% AlCl3) had transmittance of 40%. On heat-treatment at 450℃, the transparency of doped-ZnO films (with 1.0at% Al(NO3)3) were about 52%. After heat-treatment at 200-600℃ in air, the sheet resistivity of undoped-ZnO films were >5.4×105Ωcm. On heat-treatment at 600℃ in air, the sheet resistively of doped-ZnO films (with 1.0at% Al(NO3)3) were 1.7×104Ωcm, but decreased to 1.0×102Ωcm when N2 was used as atmosphere. The dielectric constant of undoped and doped ZnO films were 218~277 and 214~261 after heat-treatment at 400, respectively.
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