低電壓掃描式穿隧電流顯微鏡之研發

Abstract

本實驗欲發展一台可供研究使用的低電壓掃描式穿隧電流顯微鏡，我們根據本實驗室先前研發出的教學型掃描式穿隧電流顯微鏡(STM-Educational Version)作為參考，除了保留其本身低電壓、操作便利、可攜帶等優點，並致力於改善掃描穩定性期望能提升影像的品質，和操作更為便利等。在STM-Educational Version中操作為人為手動調整精密螺絲使探針前進到微小距離產生穿隧電流，為了使操作更為方便，因此在三年前本實驗室開始開發自動步進器。我們利用三角波電壓使蜂鳴片達到瞬間收縮的效果並結合慣性運動的原理，研發出自動步進器，但舊版自動步進器存在著不穩定的問題，在進退針動作時若沒有將步進裝置與石英棒間的摩擦力調到適當，可能會導致步進器退針動作變為進針動作，為了改善此問題，我們將連接在步進裝置上的穿隧電流線，嵌入於機構上的內部支柱，一方面可以降低電子雜訊問題，一方面還可以提高步進器的穩定性，讓步進器能正確執行進退針之動作。在避震系統方面，STM-Educational Version僅以彈簧來隔絕外界的震動，但在小範圍掃描時，仍可觀察到外界震動對掃圖的影響，因此我們除了彈簧避震系統外，還加入了磁鐵阻尼陣列，利用導體在磁場中運動會在導體內產生渦電流抵抗磁通量變化，降低外界震動對小範圍掃圖時的影響，增加掃圖的穩定性，並將Z軸解析度提升至0.1 nm。

Based on our previous designing experiences of educational version of scanning tunneling microscope (STM), we initiate a project to develop a research STM with a professional capability. The educational version of STM has several outstanding advantages, such as the low driving voltage and its high portability. Although the educational STM is easily used for students’ training, its manual operation of tip-sample approaching method and its vibration problem limit the potential for application and research. To solve the problem, we design an automatic stick-slip stepper to replace the manual operation of the tip-sample approaching screw. In addition, an eddy-current damping system is added for vibration damping that significantly reduces the vibration in a couple seconds. After the upgrade of the approaching and the vibration damping systems, the newly developed research STM show a high performance of vertical resolution up to 0.1 nm.