臺灣博碩士論文加值系統

拓樸絕緣體 (topological insulator) 是近年非常熱門的研究主題，而鉍 (Bismuth; Bi) 一直是非常適合拿來做相關實驗研究的元素之一。實驗上，已經能夠在矽基板上成功成長出鉍蜂巢狀結構 (Bi honeycomb structure)，並被預測為一二維的拓樸絕緣體。為了想更確定這樣的系統到底是不是真的 TI ，並且想更了解磁性對 TI 的影響，我們在 Bi/Au/Si(111) 上再鍍上少量的鈷 (Cobalt; Co) ，希望透過其自發性的磁場來觀察前後的各項物理性質變化。利用低能量電子繞射儀 ( Low energy electron diffraction; LEED ) 來觀察表面週期的變化，並使用掃描式穿隧電子顯微鏡 (scanning tunneling microscope; STM) 研究鈷在 Bi 蜂巢上的成長行為，加上掃描式穿隧能譜 (scanning tunneling spectroscopy; STS) 量測表面電性，藉此觀察出鍍鈷前後的差異。

Topological Insulator (TI) is popular research topic in recent years and Bismuth is always a perfect candidate for the experiments in TI. In fact, Bi honeycomb growing on Si substrate has been successfully created in the experiment and predicted as a 2D TI. To check whether this system is a 2D TI and understand the affection of magnetism, we decided to deposit small among of Cobalt on it and study the physical properties changing. By Low energy electron diffraction (LEED) we are able to see the variation of the lattice of the surfaces. Using scanning tunneling microscope (STM) and scanning tunneling spectroscopy (STS) we get to know the growth behavior of Co on Bi honeycomb and detect the surface electronic property to investigate the differences before and after the Co deposition.

論文審定書 i
誌謝 ii
Abstract iii
摘要 iv
1 簡介 1
2 原理及性質 4
2.1 拓樸絕緣體 (Topological insulator) 的介紹 . . . . . . . . . . . . . . . 4
2.2 磁性物質對拓樸絕緣體的影響 . . . . . . . . . . . . . . . . . . . . . . . 7
3 實驗儀器器器與原理 9
3.1 實驗環境-超高真空系統 (Ultra high vacuum, UHV) . . . . . . . . . . 9
3.1.1 超高真空抽氣裝置 . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2 氣體脫附 11
3.1.3 烘烤 (baking) 與去氣 (degas) 11
3.2 真空樣品表面處理 13
3.2.1 離子濺射 (Sputter) 13
3.2.2 高溫退火 (Anneal) 13
3.3 低能量電子繞射儀 (Low energy electron diffraction；LEED) 16
3.3.1 電子繞射理論 16

3.3.2 實驗儀器介紹 18
3.4 掃描式穿隧電子顯微鏡 (scanning tunneling microscope; STM) . . . 20
3.4.1 量子穿隧效應 (Quantum tunneling effect) 20
3.4.2 穿隧機率 20
3.4.3 STM儀器介紹 21
3.4.4 掃描穿隧能譜; STS 23
4 實驗結果與討論 25
4.1 乾淨的 Si(111) 的樣品處理與STM校正 25
4.1.1 Si(111) 的樣品處理 25
4.1.2 STM校正 27
4.2 Bi薄膜成長 29
4.2.1 溫度控制 29
4.2.2 時間控制 30
4.3 Co 薄膜在 Bi/Au/Si(111) 上的成長行為與結構分析 31
4.4 Co 薄膜在 Bi/Au/Si(111) 上的電子結構分析 39
5 總結 55

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