臺灣博碩士論文加值系統

本論文研發出一個改進的電化學蝕刻法並結合自動斷電電路系統製備尖銳的自旋極化掃描穿隧顯微儀(SP-STM)的鐵磁性探針。藉由使用自動斷電系統，當針尖蝕刻完成斷掉瞬間可以及時的切斷系統電源以避免探針被過度的電化學蝕刻。經由不同的直流供應電壓對於自動斷電系統的安定性之測試，發現電化學蝕刻電路系統在直流電源為8伏特時針尖的長寬比是最小。我們也研究不同種類的電解液以及其濃度對於電化學蝕刻探針的影響，然後我們發現到使用HCl溶液的蝕刻效果比KCl溶液來的好。此外，當HCl溶液的濃度為1.5 M來對鎳針尖的蝕刻效果最佳。
另外，再加上一個1.33克的塑膠方塊連接到鎳線末端，由此所製備出來的鎳探針尖端大小可達約為100 nm，並且良率顯著地上升超過40%。最後，再使用氫氟酸溶液(44%)蝕刻鎳針尖端20秒，不只能清除針尖上面的氧化層，而且還能改善探尖尖端的形状以及減少鎳針尖端曲率半徑。

In this thesis, we developed an improved electrochemical etching method combined with the automatic power cut-off system for the reproducible fabrication of sharp ferromagnetic tips used in spin polarized scanning tunneling microscopy (SP-STM). By using the automatic power cut-off circuit system, it can cut off power in time to avoid over-etching the apex of the tip. After testing different DC voltages for the circuit of electrochemical etching system, a sharp Ni tip with a lowest aspect ratio can be obtained at 8V DC voltage. We also studied different kinds of electrolytes and various concentrations of electrolytes for electrochemical etching of nickel probe, it was found that etching results of HCl solution are better than those of the KCl solution. Moreover, the best etching result of nickel tip was obtained by using the concentration of HCl at 1.5 M.
In addition, a plastic cube of 1.33 g is attached to the end of an immersed nickel wire, this leads to a sharp nickel tip with an apex size about 100nm and the reproducible rate better than 40%. Finally, the tip apex was etched in HF (40~48%) for 20 seconds, this not only removes the oxide but also improves the tip shape and reduces the curvature radius of Ni tip.

摘要.....................................................Ⅰ
Abstract.................................................Ⅱ
誌謝.....................................................Ⅲ
目錄.....................................................Ⅳ
第一章 緒論..............................................1
1.1 簡介...............................................1
1.2 文獻回顧............................................3
1.3 研究動機...........................................10
第二章 掃描穿隧顯微儀原理..................................13
2.1 掃描式穿隧顯微儀的工作原理...........................13
2.1.1 量子穿隧效應...................................14
2.1.2 探針對STM解析度的理論...........................17
2.2 自旋極化掃描穿隧顯微儀的工作原理......................24
第三章 高解析度磁性鎳探針之製備的原理與儀器裝置...............27
3.1 高解析度探針之定義...................................27
3.1.1 探針的長寬比 (aspect ratio).....................28
3.1.2 探針尖端的曲率半徑...............................30
3.2 磁性鎳探針的優點.....................................32
3.3 電化學蝕刻法的原理...................................33
3.4 電化學蝕刻法的儀器裝置...............................35
3.5 磁性鎳針尖的製備....................................40
第四章 實驗結果與分析....................................42
4.1 蝕刻條件(1)........................................42
4.2 蝕刻條件(2)........................................49
4.3 蝕刻條件(3)........................................54
4.4 蝕刻條件(4)........................................59
4.5 蝕刻條件(5)........................................65
4.5.1 質量1.3358克改變HCl濃度........................65
4.5.2 質量0.8762克改變HCl濃度........................66
4.5.3 濃度1.5M的HCl改變質量..........................67
4.5.4 質量1.3358克使用濃度1.5M的KCl..................67
4.6 蝕刻條件(6)........................................78
第五章 討論與未來改進....................................83
第六章 結論..............................................88
參考文獻.................................................89

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