The measurement and analysis about ion current of single atom tip
| Autor: | Hsin-Yin Yeh, 葉昕穎 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 This study is about measuring ion current of single atom tip by using micro-channel plat and Faraday cap with field ion microscope and improving its application. The experiment has two parts : iridium covered tungsten tip and pure iridium tip. For iridium covered tungsten tip, after annealing to 870K~1080K several times,(111) would facet to a pyramid structure with one-atom-top. Because there is only one atom on the top, the field ion current would befocus. In this study, we change the tip radius to investigate how to raise the field ion current per unit area.The investigationshowed that if the radius is larger, more image gas atom could adsorb the surface. It’s easier to supply with ions, so the field ion current could be larger. But the increasing range of ion current would go down because of the raise of shank angle. For iridium tip, after covering oxygen and annealing to 780K, (210) would facet to a pyramid, but the range of annealing temperature is narrow. If the tip temperatureover 780K, the surface would become equilibrium structure which is caused crest line between (311),(111),(100) and (110).Otherwise, iridium (110) easily cause (1×2) or (1×3) restructure after annealing. Miss rowcould change the faceting pyramid structure, andlet the formation of single atom tip become more difficult. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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