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Abstract. Strong, artificial pinning centres are required in superconducting films of large thickness for power applications in high magnetic fields. One of the methods for the introduction of pinning centres in such films is substrate decoration, i.e., growing nanoscale islands of certain materials on the substrate prior to the deposition of the superconducting film. Two other methods are building up a layered distribution of a second phase and homogeneous incorporation of second phase inclusions from a compositional target. In this paper, we compare the effectiveness of these methods in terms of the type of the self-assembly of nanoparticles. The comparison is made over a large set of YBa 2 Cu 3 O 7 films of thickness up to 6.6 µm deposited with Au, Ag, Pd, LaNiO 3 , PrBa 2 Cu 3 O 7 , YBCO, BaZrO 3 and Gd 2 Ba 4 CuWO y nanoparticles. It is found that substrate-decoration self-assembly is able to provide higher critical current in low magnetic field than the incorporation of homogeneous second phase in the sample microstructure. By specific modification of substrate decoration we achieved the self-field critical current per centimetre of width of 896 A/cm at 77.3 K and 1620 A/cm at 65 K in a film of thickness of 4.8 µm. IntroductionHigh-current superconducting applications depend strongly on the performance of superconducting tapes. Superconducting tapes, for example, are expected to find a wide use in power transmission lines, magnets, motors, generators, transformers, fault current limiters etc. In these applications they can be exposed to a high magnetic field. To increase the in-field performance of the tapes, it is necessary to incorporate into their microstructure a very dense, nanometer scale, array of pinning centers. A range of different methods for creating such an array using nanoparticles has been suggested and explored. Among these methods are substrate decoration [1], a quasi-superlattice approach [2] and volumetric addition of a secondary phase [3]. Self-assembly of nanoparticles plays an important role in each of these techniques. The first two methods represent two-dimensional (2D) and the third a three-dimensional (3D) approach to self-assembly.

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