Investigation of the effect of thermal cycling on the device performance of YBa2Cu3O7−δ DC-SQUIDs
Makaleler > Tam Makale · 2007
Yazarlar: I Avci, B P Algul, A Bozbey, R Akram, M Tepe, D Abukay
Superconductor Science and Technology, Uluslararası, Wos, 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 YBa 2 Cu 3 O 7−δ (YBCO) direct current superconducting quantum interference devices (DC-SQUIDs) fabricated onto 24° SrTiO 3 (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 µm-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.