| Summary: | 博士 === 輔仁大學 === 應用科學與工程研究所博士班 === 98 === Fluorides are present used to accomplish optical coatings for UV and deep UV range applications. Many techniques such as thermal evaporation, ion beam sputtering, electron-beam evaporation, magnetron sputtering, and ion-assisted deposition (IAD) are applied to improve the quality of fluoride films. Nevertheless, improvements of their optical and microstructural qualities are still needed. In this study, fluoride films as magnesium fluoride (MgF2), gadolinium fluoride (GdF3) and aluminum fluoride (AlF3) were fabricated at room temperature by using a thermal evaporation method with an ion-assisted deposition technique. Using sulfur hexafluoride (SF6) as a working gas in the IAD process so that more F- ions can be created from the dissociation of SF6 gas to improve the stoichiometry of fluoride films. Furthermore, optical and microstructural properties of the films deposited by using different working gases such as argon (Ar), oxygen mixed sulfur hexafluoride (O2+SF6) and without using gas in the IAD process or using SF6 as an ambient gas to where investigated.
In this study, the optimal ion-assisted voltage and current in the IAD process were determined first. The optical properties of the films were analyzed by UV/Visible/NIR spectrophotometer, micro-spot spectroscopic ellipsometer and Fourier transform infrared spectrometer (FTIR). The microstructural properties of the films were examined by atomic force microscope (AFM), field emission scanning electron microscope (FE-SEM) and X-ray diffractometer (XRD). Moreover, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition, atomic concentrations and stoichiometry of fluoride films. The binding energy (BE) shifts of Mg 2p, Gd 4d, Al 2p, O 1s and F 1s were analyzed after spectra were decomposed by some sub-peaks using a peak fitting software. The contaminants in the fluoride films such as Ar and S atoms were also identified by XPS. The correlations among the film composition, optical properties and physical properties were also discussed.
In conclusion, it was found that SF6 used as a working gas in the thermal evaporation process with an IAD technique, three fluoride films, MgF2, GdF3 and AlF3, all showed better optical qualities, packing densities and stoichiometric structures.
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