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Transport cohérent et spectroscopie tunnel dans les hétérostructures supraconductrices

David Quirion 1
1 LCP - Laboratoire de Cryophysique
SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité : DSM/DRFMC/SPSMS
Abstract : During this Ph.D., we studied the influence of a tunnel barrier on coherent transport. The structures presented in this manuscript all contain a tunnel barrier and a superconductor/normal metal (N/S) interface. Andreev reflection takes place at the N/S interface and provides the transformation of a normal current (at one particle) into a superconducting current (at two particles). This leads to the classical proximity effect. We first studied titanium nitride/highly doped silicon contacts. The Schottky barrier at the interface limited the impact of the proximity effect. At low temperature and low voltage, we observed the enhancement of conductance due to the reflectionless tunneling. Quantitative comparison with relevant theories lead us to study heating effect in long superconductor-normal metal-superconductor (SNS) structures. Secondly, we fabricated in clean room and measured at low temperature aluminium-copper-alumina-copper (SNIN) vertical structures in the diffusive regime. This time the tunnel barrier is located in the normal metal, providing a confinement of electrons close to the superconducting interface and enhancing the proximity effect. We observed a reentrance-like behaviour at low energy. By modulating the length of the normal metal between the superconducting interface and the tunnel barrier, we measured the transition from an excess conductance to a tunnel behaviour characteristics of SIN junctions, via the opening of a gap in the normal metal. These two studies show that a tunnel barrier allows the spectroscopy of density of states but can also enlight the importance of coherent transport in mesoscopic structures.
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Contributor : David Quirion <>
Submitted on : Tuesday, September 30, 2003 - 4:16:57 PM
Last modification on : Wednesday, November 4, 2020 - 2:48:51 PM
Long-term archiving on: : Friday, April 2, 2010 - 7:32:51 PM


  • HAL Id : tel-00003439, version 1



David Quirion. Transport cohérent et spectroscopie tunnel dans les hétérostructures supraconductrices. Supraconductivité [cond-mat.supr-con]. Université Joseph-Fourier - Grenoble I, 2001. Français. ⟨tel-00003439⟩



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