| 其他摘要 | ABSTRACT
Preparation of TCO films based on ZnO by sol-gel method and
their structure characterization and properties
Hui Huang (Materials Processing Engineering)
Supervised by Prof. Xin Jiang and Prof. Chao Sun
TCO films based on ZnO not only possess comparable optical and electrical properties as ITO, but also demonstrate low cost, nontoxicity, and high stability. Especially, ZnO:F films have higher transmittance, higher mobility,stronger resistance to corrosion of hydrogen plasma, and moreover are easier to be etched than normal TCO films. But ZnO:F films were only successfully prepared by CVD technique . It is significant to exploit new and effective methods for making ZnO:F films. The research work which aims to make p-type ZnO semiconductor have made little progress. But no other than p-type ZnO with low resistance and high stability can make itself be used in photoelectric devices extensively. Sol-gel method need simple equipment and is easy for doping and making large area coating.
Firstly, undoped ZnO films were prepared by sol-gel dip-coating, when zinc acetate acted as starting material. Effects of different processing parameters on undoped ZnO films were investigated. Secondly, ZnO:F films, ZnO:N films and ZnO:(N,F) films were made by adding excessive CF3COOH, CH3COONH4 and NH4F in starting solution as doping source, respectively.Special final heattreatment was adopted to obtain the final film. Structure, component, chemical condition of elements and optical transmittance of those films were characterized by XRD, SEM, AFM, XPS and UV-Vis spectrometer.
The preferred orientation of ZnO films was influenced by solvent, sol stabilizer, pretreating and post-treating temperature. Post-treating temperature influenced the cut-off frequency in the UV region.
It was difficult to dope fluorine into ZnO:F films with post-treatment in air, when CF3COOH acted as doping source. Fluorine was successfully doped into the film, when the film was post-treated in vacuum with ZnF2 powder as oxygen consumer. But there was zinc monoacetate in addition to ZnO in the film.
ZnO:N films had less transmittance in visible region than undoped ZnO film. In addition, the absorption edge in UV region of ZnO:N films had small red shift in comparison with undoped ZnO films .
F and N were doped into the films which were post-treated at vacuum or Ar, when NH4F was added into starting solution. A small quality of fluorine atoms bonded to Zn, while large numbers of fluorine atoms bonded to C. Nitrogen atoms bonded to C or H, but no N-Zn bond existed in the films.
F and N vanished when the films were post-treated in air. However transitory existence of F and N in films influenced the growth of the films, before the end of post-treatment. Different doping quality in starting solution caused different grain sizes and different cut-off frequencies in the UV region. |
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