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研究生: 陳尚文
Shang-Wen Chen
論文名稱: 金(111)面的氧化探討
The Study of the Oxidation of the Au(111) surface
指導教授: 羅榮立
Rong-Li Lo
口試委員:
學位類別: 碩士
Master
系所名稱: 理學院 - 物理學系
Department of Physics
論文出版年: 2004
畢業學年度: 92
語文別: 中文
論文頁數: 54
中文關鍵詞: (111)氧化
外文關鍵詞: gold, Au, (111), oxidation, STM, LEED, AES
相關次數: 點閱:1下載:0
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  • 在大氣環境下以STM觀察金的(111)面,會看到表面佈滿單原子層深度的深色斑點,與其他金(111)面的氧化還原實驗的結果相當類似,我們的實驗確定了這些深色斑點的生成與大氣環境有關,如果這些深色斑點的產生確實與氧化還原的過程有關,則大氣下有尚未明白的金表面氧化機制,但我們也提出深色斑點的形成可能與其他污染物有關。
    我們以熱燈絲分解氧氣的方式氧化金的(111)面,歐傑電子能譜顯示表面確實有氧的訊號,低能量電子繞射的結果則顯示內層結構並未改變,而STM則仍能觀察表面上原有的原子台階,但表面的粗糙度增加。由加熱還原氧化物後的STM結果,我們提出金(111)面的氧化機制可能為金氧位置交換,這個結果可以進一步用在金表面的催化作用研究。
    另外我們以電場梯度造成的擴散效應解釋我們觀察到STM掃描時的加速擴散效應,並發現平台上的原子團簇及凹陷會漸趨平坦且向<1 -1 0>方向拉長,而台階邊緣形成了長條狀結構也偏好<1 -1 0>方向,與探針掃描方向無關,此方向是表面重構要釋放表面應力的方向。


    Dark pits of a monolayer depth were observed on the Au(111) surfaces by STM in ambient. Similar results were observed also in other redox experiments on the same surface. Our experiments confirmed that the formation of these dark pits is related to the ambient environment. Suppose the formation of the dark pits is a consequence of redox process, there would exist unknown mechanism by which gold is oxidized in the ambient environment. However, we could not exclude the possibility that their formation is due to contamination.
    In our studies, oxidation of Au(111) surface was carried out by exposing the surface to ionized oxygen which was produced by leaking oxygen gas through a hot filament. From AES and LEED results, oxygen was confirmed to stay at the top few layers. Although the surface is rough, atomic steps could be observed in STM images. The surface was annealed to 473 K followed by STM observation. From the change of surface morphology, the place exchange mechanism is the most probable model responsible for the oxidation of gold surface.
    The field-gradient-induced diffusion was applied to interpret the tip-induced diffusion observed on the Au(111) surface. In this observation, tiny islands and craters on the terraces and finger-like structure formed at step edges were elongated along <1 –1 0> direction. The <1 –1 0> is the direction along which the surface stress on Au(111) is released.

    摘要 誌謝辭 第一章 序論 1 1-1 研究動機 1 1-2 氧化金背景介紹 4 1-3 金(111)面背景介紹 7 第二章 儀器工作原理 9 2-1 掃描式穿隧電子顯微鏡 (Scanning Tunneling Microscope, STM) 9 2-2 低能量電子繞射 (Low Energy Electron Diffraction, LEED) 14 2-3 歐傑電子能譜 (Auger Electron Spectroscopy, AES) 20 第三章 儀器介紹與實驗操作 26 3-1 儀器介紹 26 3-1.1 實驗環境 26 3-1.2 樣品處理 26 3-1.3 實驗儀器 28 3-2 實驗操作 29 3-2.1 STM探針製備 29 3-2.2 實驗過程 30 第四章 結果與討論 33 4-1 大氣環境對金(111)面的影響 33 4-2 氧離子撞擊法氧化 35 4-3 探針引起的擴散效應 45 第五章 結論 52 參考文獻 53

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