教學用掃描穿隧電流顯微鏡之人機介面設計

Abstract

自從1980年代第一台掃描式穿隧電流顯微鏡(scanning tunneling microscope，STM)問世後，人類得以開始窺探原子面貌。目前市售研究用之掃描式穿隧電流顯微鏡，其架構包含了機械主體、真空系統、低溫系統以及電子電路，整套價格所費不貲。本實驗致力於研發低成本、操作便利之掃描式穿隧電流顯微鏡，省略了專業級機台所具備的真空系統和低溫系統外，將原本需要一、兩百伏特高電壓的掃描器，替換成僅需十伏特即能驅動的掃描器，故不需要體積龐大的高電壓電路系統，以輕巧的小型電路盒取代，使整套STM系統更具可攜性。操作方面，利用精密螺絲的轉動能達到奈米級的步進效果，再輔以監視攝影機取代肉眼直接觀察探針接近樣品的狀況，大幅度降低進針時發生撞針的機率，且樣品和探針的放置，藉由磁鐵的吸附力即可輕易地裝卸。探針以往的製作方式傷神費力且品質不一，本實驗更發展做針裝置，除了操作便利外，由電路決定自動斷電的時間亦可排除人為斷電造成的時間誤差(每個人的反應時間不一)，使得所製作的每一根探針品質一樣。再經由SEM觀察結果，針尖的尖銳程度提升了一倍。使用者可透過本實驗所發展的STM系統操作介面，從製作探針到STM實際操作，在大氣底下能輕易地得到奈米尺寸的表面影像。

Energy saving and low-voltage driven scanning tunneling microscope (STM) has been developed for the educational purpose for years in our laboratory. In this thesis, we focus on the modification to approach user friendly interface so the students can easily learn to operate it. The major modification is changing a simple mirror monitor to a CCD camera for the coarse approach between the STM tip and the sample. Additionally, the rigidity of the inner stage is strengthen and the tip/sample holders are redesigned. Further, the horizontal level measurement of the inner stage is included and two ranges of scanning areas are developed for our STM. After those upgraded redesigns and modifications, our educational-purpose STM can provide large and small scan areas of 5 by 5 and 1.5 by 1.5 □m2, respectively, with resolutions of 5 and 2 nm in XY-direction and 0.1 nm in Z-direction. Various samples are studied and STM images are presented in this thesis. In addition to the upgrade of our STM machine, we develop a STM tip maker which can produce more than four tips at the same time. The tip maker can automatically switch off the electricity for electrochemical etching thus it improves the STM tip quality in comparison with those operated manually. With these friendly interfaces, the students can easily access the educational-purpose STM and focus on study of nanoscale physics.