活性離子蝕刻製作鉈系高溫超導薄膜弱鏈接面研究

Abstract

在本研究中,採用半導體工業上的活性離子蝕刻系統,來製作鉈系高溫超導 薄膜弱鏈.我們利用電漿中的尖端放電蝕刻製作出梯面高度達3um,梯面角 度在70度以上且基板表面幾乎不受損的高品質梯狀基板然而在蝕刻薄膜方 面,我們在已建立的基礎上作進一步探討,發現將蝕刻氣體中的氬氣改為氮 氣在適當的條件下可完全乾式蝕刻薄膜.在梯狀基板上的鉈系薄膜,如果薄 膜是Tl-2223相可以表現出約瑟芬遜行為,Tl-2 223相因為本身會形成弱鏈 網路而無法有約瑟芬遜性質. It is reported here the fabrication of weak-link juntion on Tl- based superconducting thin films by reactive ion etching. Step- edged substrates were prepareed by a special way in which the plasma dischardes along a sharp mental edge.The step height could be above 3um and the step angle could be bigger than 70 degree.It was found that the substrate surfaces are almost not damaged during the etching processes.It was also found that the mixed gases of SiCl4 and N2 can be used to "real-dry" etch the Tl-based superconducting films under suitable conditions.The I- V curves of superconducting micro-bridges made in Tl-2223 films deposited on the step-edged substrates showed typical Josephson characteristics. While those for bridges made in Tl-2212 films showed no josephson characteristics at all.This phenomenon was explained with the fact that weak-link network(WLN)formed in the Tl-2212 films.