Influence of Varying Gold Nanoparticle Distributions on Structural and Superconducting Properties of Thin YBCO Films

Artificial pinning centers based on crystalline gold nanoparticles inside a YBCO matrix are rarely researched so far. Nonetheless we obtained quite promising results by incorporating such particles in superconducting films. Critical current densities of 10 MA/cm
²
at 77 K were observed by using small amounts of pinning material (less than 10 vol.%). Generation of gold nanoparticle ensemble inside a YBCO layer is a self-organized process. It takes place while superconductor deposition on a prior deposited gold seed layer. Particle sizes smaller 10 nm as well as some particles around 100 nm were observed. The positive effect on superconducting properties is known from previous investigations but especially the increase in critical current density observed so far is subject to greater fluctuations. In this work various nanoparticle ensembles were investigated directly by use of focus ion beam technique (FIB), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) in well-defined areas with known local current density. This investigation provides a direct link between gold distribution and the resulting enhancement, which can be utilized to optimise process conditions in direction of favourable particle ensembles.