Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 28: Transport - Poster Session

TT 28.3: Poster

Donnerstag, 29. März 2007, 14:00–17:45, Poster A

Transport measurements on nanostructured point contacts of quench-condensed Ag — •Torben Peichl, Marcel Spurny, Michael Burst, and Georg Weiß — Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany

We report on the successful fabrication of nanostructured point contacts of disordered Ag. In the first preparation step we used electron beam lithography and SF₆ plasma etching to obtain nano-sized holes in an insulating silicon nitride membrane. Subsequent evaporation of Au onto one and Ag onto the other side of the membrane resulted in metallic point contacts. Highly disordered Ag point contacts were achieved by quench-condensing Ag films at low temperatures <10K.

Electronic transport properties of these point contacts were studied by measuring the differential resistance using lock-in methods. Our results showed distinct non-linear behavior in the region around ± 1mV so-called zero bias anomalies, which are usually attributed to two-level tunneling. We also noticed spikes at higher voltages which may be related to reversible conductance transitions.

In principle, we could obtain very reproducible conductance behavior of certain sample series. However, with almost equal preparation conditions we sometimes observed huge differences between our samples. We therefore studied in more detail the geometries of our point contacts by employing focused ion beam cutting and SEM imaging.