臺灣博碩士論文加值系統

本文中將利用超高真空掃描探針顯微鏡研究關於銀原子吸附在矽(111)-7×7重構表面上的各種現象。首先觀察低蒸鍍量下銀原子在矽(111)-7×7重構表面上的吸附影像為一個較亮的三角形半單位晶格，當原子吸附在矽(111)-7×7 faulted半單位晶格中，三個角落上層原子會較亮，而吸附在unfaulted半單位晶格中時為三個中央上層原子較亮。接著藉由降低基板溫度至81K以降低銀原子在半單位晶格中跳動的速率，證實所觀測到的的確是單一銀原子吸附的情形，並且提出單一銀原子在半單位晶格中跳動機制的模型。接著觀察高溫(348K~398K)時，銀原子在矽(111)-7×7重構表面半單位晶格之間跳躍(jump)的動態研究。我們觀察到兩個銀原子跳到同一個半單位晶格中再分開的現象，也藉由Arrhenius equation證實所觀測到的銀原子並未產生鍵結，只是單純的跳躍到同一個半單位晶格中。最後則是利用高溫實驗中，在不同溫度下銀原子的跳動速率，搭配Arrhenius plot計算出單一銀原子跳出faulted半單位晶格的活化能Ea=0.93±0.04 eV、頻率係數Ra=1010.68±0.49 Hz；跳出unfaulted半單位晶格的活化能Ea=0.81±0.05 eV、頻率係數Ra=109.65±0.6 Hz。

The adsorption and the dynamics of silver atoms on the Si(111)- 7×7 surface were studied respectively using a variable temperature scanning probe microscope. Single silver atoms adsorbed on 7×7 unit cells to form bright triangles at room temperature. When a single silver atom adsorbed in a faulted half unit cell, three corner adatom looked brighter than usual. When it adsorbed in an unfaulted half unit cell, three center adatoms looked brighter than other adatoms. The dynamics of single silver atom hopping within a half unit cell were also studied at the temperature of 81K. A model regarding to a hopping mechanism for a single silver atom hopping within a faulted and an unfaulted half unit cell was proposed respectively. The dynamics of silver atoms jumping between different half unit cells was studied at temperatures between 348K~398K. A series of STM images revealed that two silver atoms sometimes jump into a same half unit cell. However, they never found to form a stable piece in our observation. The activation energies and pre-exponential factors for single silver atoms jumping out of faulted and out of unfaulted half unit cells were finally determined by Arrhenius plots.

致謝辭......................................................6
摘要........................................................8
Abstract....................................................9
目錄.......................................................10
圖表目錄...................................................11
Chapter 1 緒論.......................................12
1.1 前言與研究動機.....................................12
1.2 研究目的及內容.....................................13
Chapter 2 原理簡介...................................14
2.1 掃描穿隧顯微術 (Scanning Tunneling Microscopy, STM)14
2.2 矽(111)-7×7表面重構................................16
2.3 Arrhenius equation 與 Arrhenius plot...............18
Chapter 3 儀器架構與實驗方法.........................21
3.1 儀器架構簡介.......................................21
3.1.1 JSPM-4500A超高真空掃描探針顯微鏡...................21
3.1.2 K-cell蒸鍍鎗.......................................22
3.1.3 低溫冷卻系統.......................................23
3.2 試片規格...........................................24
3.3 探針製備與清理.....................................25
3.4 樣品處理條件.......................................27
3.5 樣品蒸鍍條件.......................................28
3.6 STM高溫實驗........................................28
3.7 STM低溫實驗........................................29
Chapter 4 結果與討論.................................30
4.1 銀原子常溫吸附.....................................30
4.2 低溫實驗結果.......................................35
4.3 單一銀原子在HUC中的運動機制模型....................38
4.4 銀原子高溫下在HUC之間跳動的現象....................39
4.5 兩個銀原子跳入同一個HUC中的現象....................41
4.6 高溫動態實驗與銀原子吸附在HUC的表面活化能計算......44
Chapter 5 結論.......................................46
5.1 單一銀原子在矽(111)-7×7表面上吸附情形..............46
5.2 單一銀原子在HUC之中運動機制的模型..................46
5.3 單一銀原子在HUC之間跳動與表面活化能................47
參考資料...................................................49

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