單根氧化釕奈米線電子傳導特性之研究

Abstract

由於現今奈米技術蓬勃發展，特別是在電子元件的製作上，都已邁入奈米尺度的挑 戰，許多古典的理論已不適用，因此電子的傳輸性質必須加入量子力學的修正，而量子 相位相干現象也是一個被注重的研究題目。文獻上已指出普適電導漲落屬於一種量子相 位相干的現象，而且因其對雜質的移動很敏感，導致原子或次原子級的雜質移動可直接 被觀察。 本篇論文針對 RuO 2 奈米線，在單根奈米線上製作四根電極，並利用四點量測技術 避免掉接點電阻的影響，進一步確實量測材料本身的電性，然後利用液氮與液氦的特性， 將樣品從室溫降至低溫(<4 K)，觀察樣品電阻隨溫度下降而減少，與一般金屬反應一樣， 因此我們可知此材料為少數具有導電性的氧化物。另外，我們低溫中探討其電子傳輸電 性，並輸入大電流，嘗試將晶格重新排列，再利用先後的電阻與溫度之間的關係，判斷 其缺陷減少，並觀察普適電導漲落的效應改變，以此推論普適電導漲落大小，與材料的 缺陷多寡有關。 此實驗只是初步觀察到此現象，在電流的改變與材料本身的性質與尺度需如何搭配， 才可以有效地改變缺陷，這方面還需要更多的實驗去歸納與討論。

Recently, nanotechnology develops very fast, especially in electronic devices. The classical theory can not explain what we find in nano-devices. Electronic transport properties need to consider quantum correction. Quantum interference phenomenon like universal conductance fluctuation has been found to be very sensitive to mobile impurities in nano-structures. We use the electron-beam lithography process to make four-probe contacts onto individual RuO 2 nanowires. By using four-probe measurement method, the contact resistances can be avoided. We use a standard 4 He cryostat to cool the sample and measure the temperature-dependent resistance of the samples. The metallic behaviors of the RuO 2 nanowires are found. We also measure the time-dependent resistance at several temperatures. After the pristine run, we find that the sample resistance can be changed by applying a higher current density. The temperature- and time-dependent resistances of the sample are then measured again. The results are compared. It is found that both behaviors are very different before and after the change. It is conjectured that the impurity configuration inside the sample is modified. However, more investigations are needed to clarify the exact mechanism of the modification.