Crescimento e caracterizacão de filmes finos supercondutores de chumbo

Abstract

Lead thin films are attractive for fundamental research in superconductivity and practical applications due to their relatively high critical temperature and behavior as a type II superconductor. Consequently, achieving high-quality films by controlling thermodynamic parameters during their growth is important for enhancing superconducting properties. Previous studies have demonstrated that lead films deposited by thermal evaporation at room temperature exhibit large and disconnected grains. On the other hand, when the deposition occurs with the substrate maintained at liquid nitrogen temperature, the films present smaller grain sizes and higher homogeneity. Motivated by these reasons, our work investigates the growth of lead films with the substrate maintained at different temperatures to analyze the resulting microstructural and superconducting properties. Although the film grown at 77 K exhibited superior microstructural quality (smaller grains and almost no porous), the magnetic shielding capacity of the film deposited at room temperature is higher. We also designed and tested a heating device to control the temperature in the chamber. Furthermore, we obtain the local magnetic flux density, current density, and magnetization in smooth and avalanche regimes using transformations of the gray-intensity images obtained using the Magneto-optical imaging (MOI) technique.