以雷射蝕鍍法製備多層高溫超導薄膜之研究

Abstract

本論文將報告如何以雷射濺鍍法在釹鎵氧化物(NdGaO3)基板上製備多層高 溫超導薄膜.目前,本實驗室利用脈衝雷射蒸鍍技術在NdGaO3基板上成功地 成長釔鋇銅氧超導薄膜,其成果如下:在臨界溫度為 Tco=92K,臨界電流密 度(Jc)在77K時更高達8*10MA/cm2,尤其是釔鋇銅氧薄膜表面的平整度,經 由原子力顯微鏡(AFM)獲知其表面高低崎嶇相差不過5nm.利用這些已知之 經驗,進而用以製作超導/絕緣/超導的多層薄膜結構,輔以掃瞄式電子顯微 鏡,掃瞄穿隧式電子顯微鏡和 X-光繞射分析來探究其結構特性與傳輸性質 之關係. We have investigated some of the fundamental parameters involed in preparing YBCO/(I)/YBCO/NdGaO3 multilayer super- conducting thin film by using KrF Excimer pulsed laser. For single layer YBCO directly deposited onto NdGaO3 single crystal substrate, high quality film were obtained; with Tco =92K, Jc(77K)>8*10MA/ cm2. In particular, due to the optimiza- tion of deposition condition and the near perfect lattice matching between YBCO and NdGaO3, the surface topography of the obtained film, as revealed by atomic force microscopy (AFM), was extremely smooth (with roughness smaller than 5nm over 3 micrometer scanned length). With the results accompli- shed, we have also proceeded to deposited PBCO, as well as NdGaO3 as the insulating layer. It was found that the choice of these intermediate layer of the aimed multilayer structure, has a profound effect on the deposition of the subsequent superconducting layer. The detail characterizations of the microstructure analyses, and transport property measurements were performed to delineate the interplays between the growth- structure-properties.