Tunneling and Transport in Mesoscopic Structures
Final rept. 1 Mar 92-28 Feb 98
MINNESOTA UNIV MINNEAPOLIS SCHOOL OF PHYSICS AND ASTRONOMY
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A combination of electron beam lithography, reactive ion etching and low temperature vapor deposition was employed to produce ultra-small one- and two-dimensional arrays of tunneling junctions, and wires of small cross sectional area. The original goal, the production of side-by-side junctions, with tunneling occurring between metal electrodes in a plane rather than through an insulator could not be realized. Transport properties of wires with extremely small cross-sectional areas were studied. Tunneling junctions with solid inert gas barriers and metallic electrodes were prepared. The motivation for this work was to produce junctions on high temperature superconductors with robust barriers whose processing did not involve chemical reactions at the interface. Our approach was successful, although tunneling resistances have thus far been too high to observe the energy gap in a superconducting electrode. Heterostructures of cuprate superconductors and manganite ferromagnets were grown by MBE. The suppression of critical currents and critical temperatures by spin injection was observed, and the interfacial resistance across the boundary between the ferromagnet and the superconductor investigated. The effects observed are believed to be a consequence of the high degree of spin polarization in half-metallic manganite films, and may be the basis for a new superconducting device technology.
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