| 摘要: | 奈米碳管在1991年被發現之後，由於其獨特的物理及電學性質，成為一新興的奈米材料。然而目前能夠看到碳管外觀形貌的工具，不外乎是各種先進的顯微技術，如掃描式探針顯微鏡、掃描式電子顯微鏡、穿透式電子顯微鏡等等，而這種顯微技術通常有著諸多限制以及其不便性。因此，對於能夠快速觀測到奈米碳管以鑑別出實驗的結果，也是個相當重要且實用的議題。 在本文中，我們嘗試利用傳統的光學顯微鏡來觀察奈米碳管，並加以簡單的定位之後，便能夠較為準確且省時地使用原子力顯微鏡找到碳管的蹤跡，以利進一步的量測或操控。 在過程當中，發現到一些有趣的現象：碳管的光學影像會隨著樣品放置的時間不同，而有碳管從看不見，接著慢慢浮現，而後又消失的情形。這個現象，我們假設是表面自然形成的水膜所引起的。更進一步的，我們嘗試改變溼度這項參數，觀察影像的變化。我們發現，溼度的高低，也會影響碳管的光學影像。 對於碳管的周圍似乎較容易吸收一層水膜的現象，我們嘗試著用原子力顯微鏡在矽基板上的局部氧化微影術來做間接的測試。從原子力顯微鏡的初步觀察中可發現，氧化矽的條紋在低濕度時似乎是從底下將碳管抬起；而較高濕度時，氧化矽的條紋是跨越過碳管上方。 另外在碳管的操控方面，利用在空間中介電泳的方式將碳管沾附到針尖上，形成尖端非常細尖的碳管探針。而在平面上，使用原子力顯微技術也能夠達成在平面上搬運或切斷碳管之目的。這兩種操控碳管的方式，對於製作奈米元件，預期將有不錯的發展空間。 我們對於這些現象的觀察與理解，期望對之後的碳管研究，甚至對於其他一維奈米線的研究，能夠有所幫助。 Since it was discovered in 1991, carbon nanotube (CNT) has become a rising nano-material because of its unique physical and electrical properties. We can use several kinds of advanced microscopes such as scanning probe microscope (SPM), scanning electron microscope (SEM), and transmission electron microscope (TEM) to observe CNTs. However, these microscopes often have a lot of constraints and they are often labor-demanding. Therefore, it is a very important and practical topic to observe CNTs in a more convenient fashion. In this article, we try to observe CNTs by using traditional optical microscope (OM), and to locate the position at the same time. Thus we can find out CNTs rapidly by atomic force microscope (AFM), and it is helpful for further measuring and manipulation. In the process, we find some interesting phenomena: The OM image of CNTs can’t be observed at first, and then appears as time goes, and finally disappears again. We propose that this phenomenon is caused by the liquid film on the surface. Further, we find the relative humidity (RH) will also influence the CNTs’ OM image under the same mechanism. We try to practice AFM lithography on CNTs / Si to test the effect of H2O film indirectly. At low RH, the oxide stripes look like to be underneath the CNTs. However, at high RH, the stripes look like to stride across the CNTs. Besides, we made some attempt on CNT manipulation. In a 3-D version, CNTs can be attached on the tungsten tip by dielectrophoresis. In a 2-D version, CNTs can also be moved or cut using an AFM tip. These manipulation methods are expected useful for nano device. We hope that the discovery and our understanding of these phenomena can be useful for future research on CNTs, and other 1-D nano wire as well. |
