指導老師：林克默 博士 學 生：楊顯奕 報告日期：

Outline 1. Introduction 2. Experiments 3. Spectroscopic ellipsometry 4. Results and discussion 5. Conclusion

Introduction Among many deposition techniques for ZnO films [1-4], the sol-gel method is not only simple and low-cost for coating large area high quality TCO films;it also enables us to tailor the film properties with the chemistry of the sol-gel synthesis. Unfortunately, sol-gel derived crystalline structure suffers quality limitation regarding electrical and optical properties. Unfortunately, sol-gel derived crystalline structure suffers quality limitation regarding electrical and optical properties.

However, several studies reported that the ZnO film properties can be improved by optimizing deposition parameters such as the preparation and annealing conditions [1, 2] The relation among the deposition parameters, microstructure and optoelectrical properties of ZnO films is to be further understood and clarified. Particularly in the sol-gel procedure, different nucleation and growth processes can result in similar conductivity values [4].

Experiments Two kinds of samples were prepared. Similar to the deposition method in [4], the first kind of samples was prepared by using a tube furnace. The ratio of Al/Zn atoms were 0.75 and 1.0 at.%. Solution A was without any MEA. In solution B and C, monoethanolamine (MEA) was added as stabilizer. The molar ratio of MEA:ZnAc in solution B was 1:1; the pH value was 7.4. The molar ratio of solution C was 4:1, and the pH value was Solutions A, B, and C were heated at 45 °C for 3 h respectively.

After spin-coating, the silicon substrate was dried at 70 °C for 10 min in a furnace and underwent pre-heat treatment in RTA at 600 °C for 10min. After repeating this procedure for 6, 10 and 15 times, postheat treatment was carried out under vacuum (~1 mTorr) at 600 °C for 1 h. For solution A, B and C, samples A, B, and C were respectively marked.

Spectroscopic ellipsometry Two modeling strategies of SE technique were used in this study. The first modeling process is so-called GenOsc model which essentially includes Cauchy model, point-by-point approxima-tion and oscillator model [6]. The Cauchy model describes the dispersion of film refractive index as a slowly varying function of wavelength with an exponential absorption tail.

In the second modeling process, it is assumed that the AZO films were fully transparent for certain spectra. So only the Cauchy model is needed for the fitting processes. This modeling process was applied to the second kind of samples. Where n d is the refractive index of pore-free ZnO, and n f the refractive index of the AZO film.

Results and discussion Figure 1 shows the SE fitting results of a 4-layer sample fabricated with the tube furnace. The GenOsc model was applied successfully. The GenOsc model was applied successfully.Though film thickness and refractive index could be obtained,the deviation in the VU region became very obvious as the film thickness increased. Figure 1 SE fitting result, 4-layer, Al/Zn = 1.0 at.%.

Figure 2 Relative index and relative density in dependence on layer number obtained with SE, Al/Zn = 1.0 at.%.

Figure 3 Comparison of film thickness measured with SE and SEM.

Figure 4 The cross-section of sample B, 15-layer.

Figure 5 XRD patterns of samples A.

Figure 6 Comparison of the thicknesses of samples B.

Figure 7 Comparison of the thicknesses of samples A, B and C.

Conclusion 在這項研究中， SE 對 AZO 薄膜光學模型成功建立，用來衡 量薄膜厚度以及相對密度。 薄膜厚度測量的 SE 和 SEM 是一致的。 SE 的測量結果表明， 在多塗層工藝，薄膜變得更緻密。相較於 X 射線衍射搖擺 曲線法光學常數和掃描電鏡對薄膜的厚度， 這項研究使我們能夠表徵沉積 AZO 薄膜用更快，更簡單的 方法。

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