單根錫摻雜氧化銦奈米線的普適電導漲落

Abstract

ITO 是一種具透光性的良好導體，被廣泛應用在顯示面板。我們量測ITO 奈 米線的磁電阻後發現，在低溫條件下，ITO 奈米線帶有明顯的弱局域效應，我們 利用弱局域理論擬合出不同溫度下的相位破壞長度，得到很合理且準確的結果。 量測磁電阻的過程中，我們同時觀察到另外一種有趣的量子干涉效應：普適 電導漲落。我們發現在低溫下的磁電阻數據，都帶有一些隨溫度降低而變大的非 週期性電阻漲落。這些漲落大小以電導表示，都是在e2/h 的大小。而且漲落的 圖案，在低溫下是可以重複量測的，這是普適電導漲落很重要的特色，而漲落的 圖案反應了雜質與缺陷的組成。我們把樣品升回室溫，再下低溫量測後發現，漲 落的圖案改變了，這說明了室溫的熱能改變了ITO 的雜質與缺陷位置。 我們知道弱局域效應是很成熟的理論，擬合出來的結果也很準確，因此我們 利用弱局域效應所擬合出來的相位破壞長度，和普適電導漲落算出來的相位破壞 長度作比較。粗略的來說，我們得到一致的結果，兩個理論的部分結果是吻合的。 但是普適電導漲落沒辦法算出比較準確結果，這需要再進一步的討論。

ITO is a good conductor with high optical transparency, and widely used in display panels. We measured the magnetoresistance of ITO nanowires and found that at low temperature conditions, ITO nanowires have a significant weak-localization effect. We use the weak localization theory to fitting dephasing length at different temperature, and to be very reasonable and accurate results. From the magnetoresistance, we also observed another interesting quantum interference effect: Universal Conductance Fluctuations. We found that the magnetoresistance data have some aperiodic resistance fluctuations at low temperatures, and these fluctuations increase as temperature decrease. The size of the conductance fluctuations is in the order of e2 /h. And the fluctuation pattern is Reproducible at low temperature, which is the important feature of UCF. Fluctuation pattern reflects the composition of impurities and defects of sample. We put the sample back to room temperature and cool down again, we found that the fluctuation pattern changes under low-temperature measurements, indicating that the heat of room temperature could changes the position of the ITONWs’ impurities and defects. We know that weak-localization effect is a very mature theory, the results of fitting is very accurate, so we use weak-localization effect to fitting out of the dephasing length, and compare with the dephasing length which calculated from UCF theory. Roughly speaking, we got a consistent result,and some results of two theoretical are not contradictory. But no way to calculate the universal conductance fluctuations in a more accurate result, which requires further discussion.