c-Axis correlated extended defects and critical current in YBa2Cu3Ox films grown on Au and Ag-nano dot decorated substrates

We report measurements of critical current in YBa2Cu3Ox films deposited on SrTiO3 substrates decorated with silver and gold nanodots. An increase in critical current in these films, in comparison with the films deposited on non-decorated substrates, has been achieved. We argue that this increase comes from the c-axis correlated extended defects formed in the films and originated from the nanodots. Additionally to creating extended defects, the nanodots pin them and prevent their exit from the sample during the film growth, thus keeping a high density of defects and providing a lower rate of decrease of the critical current with the thickness of the films. The best pinning is achieved in the samples with silver nanodots by optimising their deposition temperature. The nanodots grown at a temperature of a few hundred °C have a small diameter of a few nanometres and a high surface density of 1011-1012 particles/cm2. We give evidence of c-axis correlated extended defects in YBa2Cu3Ox films by planar and cross-sectional atomic force microscopy, transmission electron microscopy and angle-dependent transport measurements of critical current.