| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 103 === In recent years, the transition metal nitride film has been widely used for protecting the surface of the materials and improving the life time of molds and cutting tools. The molds require higher hardness, toughness and adhesion in the future. Considering the business, to find the thin film both with performance and appearance is a major issue.
In this study, coatings of (TiZrHf)N with various working pressure are deposited by reactive radio frequency magnetron sputtering. First, the author tried to find the best parameter by changing the working pressure of sputtering and studying the relationship among working pressure, the structure and properties of the coatings. Then coatings of (TiZrHf)N doped Si with various silicon content are deposited by reactive radio frequency magnetron co-sputtering. The variation of the silicon content is consequently only achieved by using different silicon power.
The structure, texture and grain size of the coatings are determined by X-ray diffraction (XRD). The chemical composition is obtained by X-ray photoelectron spectroscopy analysis. The properties of coatings, hardness, resistivity, reflectivity and color are measured by nano-indenter, Hall effect measurement, and UV/VIS/NIR spectrometer. The morphology is investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
From SEM investigations and XRD analyses, the structure of (TiZrHf)N coatings are FCC with [111] orientation columnar structure, the crystallite sizes of are observed to be below 40 nm. XPS analysis shows the compositions of coatings are independent of working pressure. The hardness and resistivity of the coatings decrease with working pressure from 47.9 GPa to 15.4 GPa and from 70 μΩ-cm to 1.7×104 μΩ-cm. The reflectivity decrease with working pressure and the colors become darker.
Thin silicon concentration of the coatings of (TiZrHfSi)N varies between 0 and 10.06 at.%. TEM investigations and XRD analyses show that the addition of Si to (TiZrHf)N coatings transforms the [111] oriented columnar structure into amorphous structure. XPS analysis shows the presence of silicon nitride, while electron and X-ray diffraction results do not suggest the presence of crystalline Si3N4. This result clearly indicates that these films have a composite structure consisting of (TiZrHf)N nanocrystallites embedded in amorphous silicon nitride. The hardness of the nc-(TiZrHf)N/a-SiNx coatings reaches 48.6 GPa. The resistivity decreases with silicon content from 53 μΩ-cm to 6.5×103 μΩ-cm. The reflectivity decrease with silicon content and the colors change from gold to gray.
The oxidation behavior of reactively sputtered (TiZrHfSi)N thin films was investigated for oxide formation in air in the temperature range of 773-1273K. In this study, the Orthorhombic Ti(Zr,Hf)O4 structure for oxidized (TiZrHfSi)N was observed. The cross-section morphology of the coatings investigated by scanning electron microscopy (SEM) shows that oxidation thickness decrease with silicon content. The results from scanning electron microscopy (SEM) indicate the oxidation resistance improves with silicon content. And the appearance of coatings after annealing become colorful.
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