| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 95 === This thesis is focused on characterizing the mechanical properties of the thin film as function of grain size, defect and fabrication process, and investigating the effect of mechanical properties on formation of direct nanoimprint technique. Aluminum thin films will be used as the transferred material and the grain size and microstructures can be controlled by means of different deposition process and parameters. In order to analyze film thickness, internal defects, and composition, TEM and EDS are employed after the thin-film deposition process. The relationship between microstructures and mechanical properties of thin films can be characterized by nanoindentation experiments. Subsequently, formation height will be applied to analyze the formation qualities in the nanoimprint process and it can be compared with the mechanical properties of thin films. In addition, formation mechanism will be understood via observing microstructures of thin films after imprint process by TEM analysis. For the purpose of analyzing the adhesion behavior between thin film materials and silicon molds, EDS will be performed to detect the composition of the mold after imprint experiments.
Base on the experimental results, the following phenomena can be observed. Aluminum thin films with amorphous crystal structure and grain size between 5 to 65 nm could be achieved by ion-beam sputter deposition using different ion-beam voltage. At the same film thickness, lower hardness is observed when the grain size increases and this phenomenon is called Hall-Petch effect. The hardness of amorphous thin film is very high because its properties are similar to aluminum oxide. When the grain size of the thin film increases, the formation height is better and formation ratio could be used to estimate the surface topology of deformed thin films. Surface topology of deformed thin films should be single peak when the formation quality is good. Otherwise, it will be dual peak. Dislocation defect could be observed in the deformed thin films with 110 nm grain size but not in the thin films with 15 nm grain size. It could be concluded indirectly that dislocation motion is the dominant plastic deformation mechanism for the thin films with large grain, whereas grain boundary sliding is the major formation mechanism for the small grain materials. According to the EDS results, there’s no aluminum composition being found on the silicon molds and the adhesion behavior between molds and thin films could be negligible.
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