Millimeter wave surface resistance and London penetration depth of epitaxially grown YBa2Cu3O7−x thin films

✍ Scribed by N. Klein; G. Müller; S. Orbach; H. Piel; H. Chaloupka; B. Roas; L. Schultz; U. Klein; M. Peiniger

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 188 KB
• Volume: 162-164
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(89)90810-1

✦ Synopsis

The surface impedance of several c-axis oriented YBa2Cu3O7 thin-film samples was measured in a copper host cavity at 87 GHz between 4.2 K and 300 K. High aualitv films between 0.17 urn and 0.8 um In thickness have been grown epitaxially on SrTiO3 by pulsed excimer laser~ablation. The partial penetration of the electromagnetic fields into the substrate leads to an enlarged surface resistance Rs and reactance Xs. By means of numerical simulations for the effective surface impedance of the film-sub&r& sandwich, the true-values for Rs and Xs of YBa2Cu307-x are extracted from the data. The best samoles show a sham drop of R. at T, CY 88 K to leas _ . __ than lcmfl at 77 K. These values exceed the best results on polycrystall& samples Gd co& close to the expectation from classical superconductors. Experimental results on Xs for different thin-film sampler are in good agreement to the numerical results if a temperature dependence of the penetration depth XlTl according to the BCS-theory in the weak coupling limit is assumed. The extrapolated X(O)-value Is (168*2O)mn.