不同厚度氮化鈮薄膜之別列津斯基-科斯特利茨-索利斯相變研究

Abstract

別列津斯基-科斯特利茨-索利斯相變（Berezinskii–Kosterlitz–Thouless transition， BKT相變）是發生於二維系統中的特殊相變。論文中藉由一系列不同厚度及生長於不同基板上的氮化鈮(NbN)薄膜，探討厚度與BKT相變之關係。從實驗結果中我們得知，生長於MgO基板上的NbN薄膜之超導臨界溫度(TC)高於生長於藍寶石基板上的。有趣的是，儘管厚度已經達到100nm厚的薄膜，依舊觀察到BKT相變，並藉由三種方法，證明了BKT相變溫度的真實性。從實驗結果中得知，我們在不同厚度的氮化鈮薄膜中均觀察到BKT相變。

The Berezinskii–Kosterlitz–Thouless transition (BKT phase transition) is a special phase transition that occurs in two-dimensional systems. In this thesis, a series of niobium nitride (NbN) thin films with different thickness and grown on different substrates are tudied. From the experimental results, we observe that the superconducting critical temperature (TC) of NbN thin films grown on MgO substrates is higher than that of NbN grown on sapphire substrate. Interestingly, even though the film has a thickness of 100 nm, the BKT phase transition is still observed.