The excess 1/f noise investigations of YBCO films on SrTiO₃ substrates are reported.The epitaxial films produced by the laser ablation are characterized by the high perfectstructure, sharp superconducting transition, strong pinning and very low excess 1/f noise.It is observed that the level at normal state depends on the dislocation density. The bestnoise properties are observed for films with the dislocation density of (8-12) disl/Μm².These films have noise Hooge-parameters of around (1.6-3)×10^-6, which is 3 order lessthan published values. The calculation of the bolometer based on investigated films,shows the possibility to reach the noise equivalent power limited by only the phononnoise in the modulating frequency range beginning above 0.1 Hz.

Thin films of the high-temperature superconductor YBa₂Cu₃O(7-δ) exhibit both a large critical current (the superconducting current density generally lies between 10 and 10 A m^-2 at 4.2 K in zero magnetic field) and a decrease in such currents with magnetic field that point to the importance of strong vortex pinning along extended defects. But it has hitherto been unclear which types of defect - dislocations, grain boundaries, surface corrugations and anti-phase boundaries - are responsible. Here we make use of a sequential etching technique to address this question. We find that both edge and screw dislocations, which can be mapped quantitatively by this technique, are the linear defects that provide the strong pinning centres responsible for the high critical currents observed in these thin films. Moreover, we find that the superconducting current density is essentially independent of the density of linear defects at low magnetic fields. These natural linear defects, in contrast to artificially generated columnar defects, exhibit self-organized short-range order, suggesting that YBa₂Cu₃O(7-δ) thin films offer an attractive system for investigating the properties of vortex matter in a superconductor with a tailored defect structure.

At low fluences, the [Sr]/[Ti] ratio of laser deposited SrTiO3 films appears to be a function of the laser fluence. The deviation from stoichiometry is remarkably constant in time. From an analysis of both the composition of the film and the irradiated target, we deduce a volume-diffusion-assisted preferential ablation process. At high fluences (above 1.3 J/cm2), stoichiometric SrTiO3 films are obtained. This is not due to a change in ablation mechanism, but follows from the fact that at 1.3 J/cm2 the calculated diffusion length of Sr within the irradiated target, becomes of the order of the ablation rate per shot.