Dissertação
Produção de filmes supercondutores de nióbio e de sistemas híbridos crescidos por Magnetron Sputtering DC
Fecha
2012-08-16Registro en:
CARMO, Danusa do. Production of superconducting niobium films and hybrid sistems grown by DC Magnetron Sputtering. 2012. 90 f. Dissertação (Mestrado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2012.
Autor
Carmo, Danusa do
Institución
Resumen
Currently, several research groups have been devoted to the production of superconducting
films. This interest lies on the facility of their manipulation, on the understanding of basic
concepts of the superconductivity and, especially, in the possibility of reducing them to
dimensions compatible to their application as devices. Therefore, there is a great technological
and academic interest in this issue. The most used material in superconducting devices is the
niobium (Nb) and its alloys. Although Nb has been known as superconductor since 1930, the
interest in excellent films of this material still remains. In this work, using a DC magnetron
sputtering technique, we have developed an experimental method that allows one to produce
superconducting Nb films of good quality - transition temperature of 9.1 K and transition width
of 0.2 K. Therefore, we performed a systematic study of the setup parameters that influences
the structural and superconducting properties of the films. In particular, we have analyzed
the evolution of the lattice parameter, average grain size crystalline and critical temperature.
Such values have been compared in a diagram. Nb films exhibit flux avalanches at certain
values of field and temperature. We have detected and visualized the occurrence of avalanches
of magnetic flux in Nb films and, in order to suppress the abrupt flux penetration, we have
coupled to the films of thickness of 200 nm, thick metal layers of aluminum, silver and copper
of different thicknesses, so called hybrid systems - Superconductor/Normal Metal. In this work
piece, two experimental techniques have been employed: magnetometry and magneto-optical
imaging. A partial suppression of avalanches in the hybrid systems has been observed.