高原子序元素的蜂巢狀結構被預期有機會展現拓樸邊緣態 (Topological edge state) 的性質。因此, 為了尋找新穎的二維拓樸絕緣體 (Topological insulator; TI) 材料，在超高真空的環境裡，我們利用電子束蒸鍍槍 (Electron beam evaporator) 在室溫下將鉍 (Bismuth; Bi) 成長至 Si(111)-√3×√3-R30°-Au 的表面上後。接著做高溫退火的動作使 Bi 重新排列成一個有序的結構。利用低能量電子繞射儀 (Low energy electron diffraction；LEED ) ，可觀察到Bi 形成 √3×√3 的週期。由掃描式穿
隧電子顯微鏡 (scanning tunneling microscope; STM) ，我們觀察到 Buckled 的 Bi 蜂巢狀結構，而 Au 的三聚物 (Trimer) 在此扮演著穩定 Bi 蜂巢的角色。為了進一步確認拓樸態是否真的存在，我們利用掃描式穿隧能譜 (Scanning tunneling spectroscopy; STS) 量測表面上不同區域間的電性。在 Bi 蜂巢的邊緣上，存在著與其他區域不同的特徵，這也提供了邊緣態可能存在的證據。

The Honeycomb structure of meatal with high atomic number was predicted as a candidate which can show the topological edge state. To find the new material having topological state, Bi atoms were deposited on Si(111)-√3×√3-R30°-Au surface by electron beam evaporate under the ultra high vacuum. After post-annealing procedures, an ordered structure of Bi was observed, showing the √3×√3 superstructure in low energy electron diffraction. From measurement of scanning tunneling microscope, Bi honeycomb was found under different sample bias. Therefore, it was confirmed that Bi formed the honeycomb structure on Si(111)-√3×√3-R30°-Au surface, and Au trimmer was the role which stablized the Bi honeycomb. To identify wether proposed topological edge state exist on Bi honeycomb, the electronic structure of different regions on surface was measureed by scanning tunneling spectroscope. At edge of Bi honeycomb, different dI/dV feature was found. It was a possible evidence to prove the topological state existing on edge of Bi honeycomb.

論文審定書 i
摘要 ii
Abstract iii
誌謝 iv
1 簡介. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 原理及性質
2.1 拓樸絕緣體(Topological insulator) 的介紹. . . . . . . . . . . . . . . 4
2.2 驗證拓樸絕體的實驗方法. . . . . . . . . . . . . . . . . . . . . . . . . 10
3 實驗儀器與原理
3.1 實驗環境-超高真空系統(Ultra high vacuum, UHV) . . . . . . . . . . 12
3.1.1 氣體脫附. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1.2 烘烤(baking) 與去氣(degas) . . . . . . . . . . . . . . . . . . 13
3.1.3 超高真空抽氣裝置. . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 真空樣品表面處理. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.1 離子濺射(Sputter) . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.2 高溫退火(Anneal) . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3 低能量電子繞射儀(Low energy electron diffraction；LEED) . . . . 20
3.3.1 電子繞射原理. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.3.2 實驗裝置. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3.3 表面重構(Superstructure) . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4 掃描式穿隧電子顯微鏡(scanning tunneling microscope; STM) . . . 26
3.4.1 量子穿隧現象(Tunneling effect) . . . . . . . . . . . . . . . . . . . . . . .26
3.4.2 成像模式. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
3.5 掃描穿隧能譜(Scanning tunneling spectroscopy; STS) . . . . . . . . 31
4 實驗結果與討論
4.1 乾淨的Si(111) 的樣品處理. . . . . . . . . . . . . . . . . . . . . . . . 32
4.2 樣品溫度校正. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.3 Au 和Bi 鍍率校正. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.3.1 Au 的鍍率校正. . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.3.2 Bi 的鍍率校正. . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.4 Si(111)-√3×√3-R30°-Au. . . . . . . . . . . . . . . . . . . . . . . 43
4.5 Bi 薄膜在 Au/Si(111) 上的成長行為與結構分析. . . . . . . . . . . . 48
4.6 Bi 薄膜在 Au/Si(111) 上的電子結構分析. . . . . . . . . . . . . . . . 58
5 總結. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

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