The Building of the Molecular Beam System
| Autor: | Ting-Wei Liao, 廖庭偉 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 We have built up a new ultrahigh vacuum molecular beam system. This system contains a molecular beam source chamber, a main chamber and a QMS chamber. Between any two of them, there is an aperture. These apertures are utilized for differential pumping, which prevents the pressure of the main chamber increase too much, when the pulsed valve operates. In order to obtain the optimized specular molecular beam, we found out the optimal conditions of the molecular beam and the optimal position for the scattering experiments. We also utilized this system to demonstrate the morphological evolution of gold nano-clusters supported by θ-Al2O3/NiAl(100) with the sample temperature. At low coverages of Au, such as 1 ML and 4 ML, the Au on the θ-Al2O3/NiAl(100) diffuses into the oxide film, as temperature varies from 300 K to 1000 K, and that makes the bare oxide surface exposed. At high coverage of Au, such as 8 ML, there are some Au nano-clusters remained on the θ-Al2O3/NiAl(100) after annealing to 1000 K and the morphology of these Au clusters is a function of the temperature: as the temperature increased from 300 K to 900 K, it is more likely the Au covered-surface became more smooth. As the temperature of the sample further increased to 1000 K, the surface became relatively rough, resulting in drop of the reflectivity. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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