Investigation of the effect of thermal cycling on the device performance of YBa2Cu3O7-delta DC-SQUIDs
Makaleler > Tam Makale · 2007
Yazarlar: Mustafa TEPE, I. Avci, B. P. Algul, A. Bozbey, R. Akram, M. Tepe, D. Abukay
SUPERCONDUCTOR SCIENCE & TECHNOLOGY, SCI Expanded İndekslerine Giren Dergi, Uluslararası, 2007, cilt 20, ss 944-949
DOI: 10.1088/0953-2048/20/10/008
Özet
We investigated the effect of thermal cycling on the operational performance of YBa2Cu3O7-delta (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) fabricated onto 24 degrees SrTiO3 (STO) bicrystal substrates. The devices under investigation consist of directly coupled DC-SQUID magnetometer configurations. Thin films having 200 nm thicknesses were deposited by dc-magnetron sputtering and device patterns were made by a standard lithography process and chemical etching. The SQUIDs having 4 mu m-wide grain boundary Josephson junctions (GBJJs) were characterized by means of critical currents, peak-to-peak output voltages and noise levels, depending on the thermal cycles. In order to achieve a protective layer for the junctions against the undesired effects of thermal cycles and ambient atmosphere during the room temperature storage, the devices were coated with a 400 nm thick YBCO layer at room temperature. Since the second layer of amorphous YBCO is completely electrically insulating, it does not affect the operation of the junctions and pick-up coils of magnetometers. This two-layered configuration ensures the protection of the junctions from ambient atmosphere as well as from the effect of water molecules interacting with the film structure during each thermal cycle.