利用飛秒脈衝雷射製備釔鋇銅氧薄膜之研究

Abstract

本論文第一部分係利用飛秒脈衝雷射沈積技術成長釔鋇銅氧薄膜於鈦酸鍶(100)基板上，調變溫度、氧壓、雷射能量、閘門重複率、閘門開啟時間等參數，比較不同條件下薄膜的品質。在最佳條件下成長的樣品具有良好的超導性質與晶格結構。藉由掃描式電子顯微鏡以及探討電阻-溫度曲線與X-ray晶格繞射的量測結果，推測出飛秒脈衝雷射的成長機制不同於準分子脈衝雷射的混合式成長，而是奈米粒子的隨機堆疊。接著測量超導臨界電流來更進一步比較飛秒雷射與準分子雷射鍍膜的差異。第二部分成功利用微波加熱系統加熱碳化矽，再對夾於其中的兩片釔鋇銅氧超導薄膜進行加熱加壓接合，接合後成功保留釔鋇銅氧薄膜的超導電性，此結果顯示接合釔鋇銅氧超導導線的可行性，將來甚至可應用於無限長超導導線的製備。

High-Tc superconductor YBa2Cu3O7-δ (YBCO) thin films with good superconducting and crystalline properties are successfully prepared on SrTiO3 (STO) substrates by femtosecond pulsed laser deposition (fs PLD). Here we present a detail study of the YBCO thin films through varying growth parameters such as substrate temperature, O2 pressure, laser fluence, shutter repetition rate, and shutter open time. The characteristics of YBCO thin films are further examined by scanning electron microscopy, atomic force microscopy, 4-point resistance-temperature measurement, x-ray diffraction, which are compared to the YBCO thin films deposited by conventional excimer-laser-based PLD. The results suggest that the growth mechanism of fs PLD is random stacking of nano-particles rather than mixed growth in excimer-laser-based PLD. The critical current density of YBCO films was measured to further compare the properties of fs PLD and ns PLD. Second part of this thesis is that by using microwave generator to heat SiC bulk and the YBCO thin films between two SiC bulks are then heated. Finally, the two YBCO films are successfully jointed with superconductivity, which will be potentially applied to prepare the long high-Tc superconducting wires.