Weak Link Formation in Thallium Borium Calcium Copper Oxide

近几个月来，高温超导薄膜的电学和材料性能有了显著的提高。然而，一种能够以有限产量生产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77 K噪声水平足够低，可以用于许多应用。不幸的是，缺乏对可重复地实现合适的I-V特性所需的处理协议的基本理解。第一阶段计划的目标是建立可靠的弱链接制造铊-硼-钙-氧化铜所需的基本加工技术。本文将研究一种利用氧化铊高挥发性的新方法。将测量薄弱环节的电流电压特性，并制定最佳加工条件。这些结果将确定可重复地制造铊-钡-钙-铜-氧化物微桥连接的可行性。这些结果将为第二阶段项目中制造有源HTSC器件（如squid和微波混合器）提供关键组件。

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.