Weak Link Formation in Thallium Borium Calcium Copper Oxide

近几个月来，高温超导(HTSC)薄膜的电学和材料性能都有了很大的提高。然而，一种能够以有限成品率产生约瑟夫森结的制造工艺尚未开发出来。已经制作的一些演示装置表明，由铊-钡-钙-铜氧化物制成的直流SQUID的77K噪声电平足以满足许多应用。不幸的是，缺乏对可重复地实现适当的I-V特性所需的处理协议的基本了解。这一第一阶段计划的目标是建立可靠的薄弱环节制造所需的基本工艺技术，以制造铊-硼-钙-铜氧化物。一种新的方法将被研究，它利用了氧化铊的高挥发性。将测量薄弱环节的电流-电压特性，并制定最佳工艺条件。这些结果将为Tl-BaO-CaO-CuO微桥中可重复制作连接件的可行性奠定基础。这些结果将提供制造第二阶段计划中的有源高温超导器件所需的关键部件，如鱿鱼和微波混合器。

The electrical and material properties of high temperature superconducting (HTSC) thin films have improved dramatically in recent months. However, a fabrication process capable of producing Josephson junctions in finite yields has yet to be developed. Some demonstration devices have been made which indicate that the 77 K noise levels of dc SQUIDs made from thallium-barium-calcium-copper-oxide are low enough for many applications. Unfortunately, a basic understanding of the processing protocol needed to reproducibly achieve suitable I-V characteristics is lacking. The objective of this Phase I program is to establish the basic processing technology required for reliable weak link fabrication in thallium-boricum-calcium- copper-oxide. A novel approach will be investigated which takes advantage of the high volatility of thallium oxide. The current- voltage characteristics of the weak links will be measured and optimum processing conditions developed. These results will establish the feasibility of reproducibly fabricating links in microbridges of thallium-barium-calcium-copper-oxide. These results will provide the key component required to fabricate active HTSC devices such as SQUIDS and microwave mixers in the Phase II Program.