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一、引言 为了得到性能良好的约瑟夫逊铅隧道结,两层铅膜间的氧化层必须均匀、致密,厚度约为10—20埃,其间没有大面积漏洞,也不允许夹杂着氧化铅以外的大颗粒杂质。但是直接观测这一势垒层的状态和铅、氧离子的扩散活动是很困难的,因而广泛采用的判据是反映了氧化层状态的宏观隧道电阻R_T。大量的实验表明,对于性能良好的结,R_T应为数毫欧到数百毫欧。在结的储存过程中,伴随着铅膜与氧化层内原子与离子的扩散,结
I. INTRODUCTION In order to obtain a well-behaved Josephson lead tunnel junction, the oxide layer between the two lead films must be uniform and dense with a thickness of about 10-20 angstroms. There are no large-scale loopholes and no inclusions other than lead oxide Large particles of impurities. However, it is very difficult to directly observe the state of this barrier layer and the diffusion of lead and oxygen ions. Therefore, the widely used criterion is the macroscopic tunnel resistance R_T which reflects the state of the oxide layer. Numerous experiments show that R_T should range from a few milliohms to hundreds of milliohms for well-performing junctions. In the junction of the storage process, along with the lead film and oxide layer of atoms and ions in the diffusion, junction