Investigation of the effect of thermal cycling on the device performance of YBa2Cu3O7-δ DC-SQUIDs
Author
Avci I.
Algul, B.P.
Bozbey, A.
Akram, R.
Tepe, M.
Abukay, D.
Date
2007Source Title
Superconductor Science and Technology
Print ISSN
0953-2048
Volume
20
Issue
10
Pages
944 - 949
Language
English
Type
ArticleItem Usage Stats
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Show full item recordAbstract
We investigated the effect of thermal cycling on the operational performance of YBa2Cu3O7-δ (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) fabricated onto 24°SrTiO3 (STO) bicrystal substrates. The devices under investigation consist of directly coupled DC-SQUID magnetometer configurations. Thin films having 200nm thicknesses were deposited by dc-magnetron sputtering and device patterns were made by a standard lithography process and chemical etching. The SQUIDs having 4νm-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 400nm 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. © IOP Publishing Ltd.
Keywords
Critical currentsEtching
Lithography
Magnetron sputtering
Molecular interactions
SQUIDs
Substrates
Thermal cycling
DC-magnetron sputtering
Protective layers
Yttrium barium copper oxides