以雷射蒸鍍法製備大面積釔系超導薄膜之研究

Abstract

本論文將雷射蒸鍍法製備大面積薄膜分成兩個主要部份。第一篇是介紹建 立大面積蒸鍍系統，我們加裝一個旋轉的平面反射鏡於脈衝雷射導光系統 中，另外也利用步進馬達來控制加熱器的轉動。在直徑35mm範圍內分佈五 片NdGaO3基板，所得到釔鋇銅氧薄膜的超導臨界溫度為88.3±0.5K，超導 臨界電流密度在77K時均大於1×10E+6 膜厚差異在±8﹪以內，從X-RAY繞 射圖可看出薄膜是接近完全c軸成長，此外SEM表面影像圖也看出其均勻性 。第二篇是介紹此蒸鍍系統應用於蒸鍍數片相同基板上長出不同厚度的薄 膜。使用AFM來觀察NdGaO3基板和經由兩種處理方式的 MgO基板上長出的 釔系薄膜，並比較由即時電阻量測的結果，藉以了解在這兩種基板上釔系 薄膜的成長機制。 We have developed a laser scanning ablation system to prepare area YBCO thin films. By using of this scanning system, the beam can scan a circle on a targer and generate plume with a about 40 mm. Five pieces of NdGaO3 substrates were attached to substrate holder, simultaneously at different locations spanning circle of 35 mm in diameter to test the uniformity achievable by method. Uniformities with the critical transition temperature 0.5K,critical current density (Jc,77K)=1~1.8*106 A/ cm2,and the in the film thickness within 8% can be readily achieved .In XRD results and SEM analysis show that the films obtained were c-axis oriented with extremely smooth surface. A further modification on this laser sanning ablation system made to in-situ deposite thin films with various thickness on substrates. As a result, these films deposited on NdGaO3 and MgO substrates have been studied by atomic force microscopy( AFM) to investigate the effects of lattice mismatch and different treatments on the growth mechanisms ofYBCO thin films.