Preparation and properties of thin film YBa2Cu3OX devices
1993; Elsevier BV; Volume: 209; Issue: 1-3 Linguagem: Inglês
10.1016/0921-4534(93)90925-g
ISSN1873-2143
AutoresG. Friedl, M. Seitz, B. Holzäpfel, B. Roas, B. Stritzker, G. Daalmans, D. Uhl, B. Hillenbrand, L. Schultz, H. E. Hoenig,
Tópico(s)Magneto-Optical Properties and Applications
ResumoAbstract Low-noise YBa 2 Cu 3 O x dc SQUIDs and flux transformers were fabricated by laser deposition. The Josephson junctions were of grain boundary type, formed by epitaxial thin filmes, covering Ar + ion milled step edge substrates. The 5 μm wide dc SQUIDs were patterned by a SiO inhibit technique. The SQUID hole was varied between 5μm ∗ 10μm and 50μm ∗ 50μm, representing SQUID inductances between 20 pH and 140 pH. The optimum transfer function δV/δΦ at the appropriate flux bias was greater than 100 μV/Φo at 77K for samples with 20 pH. The best value of the energy resolution for samples with 20 pH is ϵ n,w (f > 30 Hz ) = 6 ∗ 10 −31 J/Hz in the white noise region and dc bias modulation. The energy sensitivity was measured as a function of the SQUID inductance. The coloured noise could be reduced by one order of magnitude applying an ac-bias to the SQUIDs obtaining an energy resolution for samples with 20 pH of 3 ∗ 10 −30 J/Hz at 1 Hz. Noise contributions from conductance fluctuations or flux hopping could be seperated by measuring the equivalent flux noise as a function of the bias current. A preparation technique for thin-film input coils has been developed, in which the three epitaxial layers were patterned either by deposition through shadow masks or by Ar + ion milling. A 12 turn flux transformer with 25 μm wide lines carried a persistent current of about 1 mA for more than two hours. To fabricate a homogeneous multilayer sequence of YBa 2 Cu 3 O x -SrTiO 3 -YBa 2 Cu 3 O x on a SrTiO 3 -substrate, an off axis laser deposition geometry was established, providing smooth films without laser particulates.
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