以直流濺鍍法製備釔鋇銅氧超導薄膜於氧化鎂基板

Abstract

本實驗是以直流濺鍍製備釔鋇銅氧超導薄膜於(001)氧化鎂基板上,並且討 論製程參數對其顯微結構及超導性質的影響.我們以X光繞射分析儀.掃描 式電子顯微鏡與感應耦合電漿電子發射光譜分析儀來分析探討成長薄膜的 結構和成份,並以四極探針法測量其臨界溫度.我們發現當基板溫度在680 C至700 C時,可成長出C軸從優取向的超導薄膜.另外提高濺鍍氣體的壓力 與氬氣對氧氣的比例時,有助於減低負離子撞擊基板表面的效應,如此可得 到較佳品質的超導薄膜.雖然我們所測得的X光繞射分析圖形顯示只有C軸 垂直氧化鎂基板的釔鋇銅氧相存在,但是我們以穿透式電子顯微鏡觀察其 顯微結構,卻發現另有C軸平行於基板平面的釔鋇銅氧相和其它第二相存 在.這些第二相以X光能量成份分析儀檢驗,得知為氧化銅與氧化釔.而本實 驗在氧化鎂基板所生長的釔鋇銅氧超導膜,其臨界溫度(電阻等於零時)可 達83K,而其臨界電流在60K約為10 5 A/cm2. The present work reports a study of the effects of the deposition conditions on the microstructure and superconductive properties of YBCO thin films formed by DC magnetron sputtering plasma, and the critical temperatures were determined by four- probe method. The films were c-axis preferentially oriented with respect to (001) MgO surface at substrate temperatures 680-700 C. The resputtering effect of oxygen can be greatly reduced with a high argon-oxygen ratios and a high gas pressures. Although X-ray diffraction shows a definite c-axis alignment normal to the substrate plane, futher analysis reveals that a-axis alignment normal to the substrate plane, and numerous second phases are also observed. The second phases including CuO and Y2O3 are identified by energy dispersive X- ray spectrometer and the detailed microstructure are analyzed by transmission electron microscopy. In our work, YBCO thin films on MgO substrate attain a Tc (R=0) of 83 K and Jc of 10 5 A/cm2 at 60 K.