Identification of radio-frequency and microwave residual-loss mechanisms in YBa₂Cu₃O_{7- delta}films in a magnetic field

Abstract

The RF and microwave response of YBa2Cu307-S films on Ba,Srj-,TiOs/MgO substrates was investigated in an external static magnetic field. Films with a varying thickness, orientation and type of structure were studied in order to understand the mechanisms of RF and microwave residual losses. The measurements of surface resistance (R) as a function of the film t h i c h s s and static ( H ) and RF (H-) magnetic field are discussed. Analysis of theoretical and experimental R(H) dependences has shown that residual RF and microwave losses occur in a static magnetic field on Josephson junctions formed at grain boundaries and at microblock boundaries with trapped Abrikosov vortices and on Abrikosov vortices themselves, and are also caused by non-superconductive inclusions.

Influence of growth rate on the structural orientation of YBCO superconducting films

“…Films with c ⊥ and c orientation, grown at process parameters close to the boundary values, had a small quantity of alternatively oriented domains, and these films were characterized by microblock structure. The grain size correlated with the critical thickness of oriented film, h c , estimated at 300 nm [14]. It was shown previously [20] that Table 1.…”

“…Superconducting YBCO films were grown by DC magnetron sputtering of a stoichiometric ceramic target [7,14,[20][21][22]. Various substrates-(100) LaAlO 3 (LAO), (100) SrTiO 3 (STO), (100) MgO and a 200-300-nm-thick Ba 0.6 Sr 0.4 TiO 3 heteroepitaxial layer grown on (100) MgO plates (BSTO/MgO) were used.…”

“…The main contaminant phases in YBCO films are located at grain boundaries, especially at boundaries of microblocks having different (100) and (001) orientations [12]. These inclusions in films of mixed orientation are an additional source of residual microwave loss [13,14] and frequency noise [15]. In order to grow films possessing a minimal defect concentration it is necessary to examine the preparation factors determining the axis orientation.…”

Fabrication process and noise properties of antenna-coupled microbolometers based on superconducting YBCO films

“…x, lattice site distribution of oxygen atoms on the sublattices and finished at low temperature and ordered distribution. As shown in [25,26], epitaxial YBCO films consist of grains with low-angle grain boundaries between them. The boundaries are both a channel for exchange of oxygen atoms belonging to different CuO planes and a channel of oxygen ingress into the film and egress out the film, depending on the regime of post-growth annealing and storage atmosphere [11,26,27].…”

“…The experimental and model investigations [11,[24][25][26] led to a conclusion that YBCO film processing should be modified, especially in the initial stage of film formation. Therefore, the specific discharge power at the shutter opening time was reduced from the nominal value w to ∼0.3w.…”