Superconducting devices

We study nanofabrication in superconducting thin films to taylor new properties and device functionalities. The main idea is to comprehend the vortex interaction with nanostructures in order to improve the superconducting properties, such as the critical current density. To do so, we have collaborations within Brazil (LCN/UFGRS) and abroad (EPNM/ULg and QSP/KU Leuven, Belgium).

Current project: 

Superconductivity at different textures: sintered granulars, thin films of variable thickness and granular structures formed by simple geometric elements juxtaposed

member

This research proposal comprises three subprojects. One of them involves the production of superconducting films with different thicknesses, in addition to wedge-shaped samples (variable thickness) aiming to study thickness-dependent changes in the morphology of the penetrated flow. Furthermore, the variation of critical current density with thickness will also be investigated, through its effects on the triggering and evolution of flux avalanches. In the second subproject, devices formed by the juxtaposition of simple geometric elements will be studied, with different thicknesses and varying values of the ratio between the critical current of the junction (intergranular) and that of the individual parts (intragranular). The other subproject is aimed at studying variations in the synthesis and processing of YBa2Cu3O7-x (YBCO) in the search for favorable conditions to increasing the critical current of nanofibers - eventually transformed into powder - produced by the innovative technique called Solution Blow Spinning. Three different conditions will be studied: (i) introduction of non-superconducting Y2BaCuO5 particles; (ii) addition of nickel (magnetic) and zinc (non-magnetic) - in the YBCO matrix; (iii) variation of nanofiber synthesis using different molar masses of the PVP polymer.

Past project: 

Effects of thickness variation on magnetic flux penetration in superconducting thin films

coordinator

In the last decades, the investigation of superconducting thin films has revealed interesting aspects of the superconductivity. One of these aspects is the abrupt invasion of magnetic flux with a dendritic shape, so-called flux avalanche, which occurs due to thermomagnetic instabilities. One important parameter to trigger this phenomenon is the thickness of the thin film, which must be homogeneous throughout the specimen. So, one aim of this project is to build a rotating substrate holder with temperature controller to be installed in a high-vacuum chamber employed to conventional thermal evaporation. It will allow us to grow superconducting thin film systematically, improving the control and the quality of the thin films prepared from different materials, such as lead, tin, and Pb-Sn alloy. Uniform films with thicknesses in the range of 50 nm and 1 mm will be deposited, as well as with a gradient thickness (wedge), under different temperatures. The effects of different thicknesses in the smooth and abrupt flux penetration will be investigated by magnetic measurements (DC magnetization and AC susceptibility) and magneto-optical imaging. The structural properties of the samples will be studied by X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Energy-Dispersive X-ray Spectroscopy and Atomic force microscopy. This project is part of an effort to understand the occurrence of flux avalanches, which is an undesirable event in applications of superconducting thin films.

Recent publications: