Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: Transport - Poster Session

TT 28.2: Poster

Thursday, March 29, 2007, 14:00–17:45, Poster A

Few-atom contacts: behavior at high electric currents — •Christian Schirm, Jochen Grebing, and Elke Scheer — Fachbereich Physik, Universität Konstanz, D-78457 Konstanz

We investigated metallic point contacts arranged with the mechanical controllable break junctions (MCB) technique of gold and aluminum at high voltages up to 1 Volt. Two mechanisms that influence the electrical resistance can be observed and studied in this regime: conductance fluctuations as function of the voltage, but also atomic rearrangements that change the conductance abruptly.

Measurements with lithographically fabricated MCB were performed in vacuum at 1.5K. Statistically atomic-size contacts adopt preferred conductance values [1]. A conductance close to these values is assumed to indicate a more stable atomic confirmation of the contact. Unexpectedly we find that when increasing the current, the conductance has the tendency to increase stepwise and eventually jump to zero. A statistical analysis of 500 such cycles will be presented. As a result the preferred conductance values just before break correspond to those found in histograms recorded for small currents [1].

Also the influence of the bias voltage on the transport properties of gold MCB has been studied at ambient conditions. First histograms taken for bias values up to 400mV seem to show a decrease in the height of the first two conductance peaks while their position stays the same. This is in accordance with work using different techniques [2].

[1] B. Ludoph, J.M. van Ruitenbeek, Phys. Rev. B 61, 2273 (2000)

[2] A. Sakai et al., Phys. Rev. B 72, 045407 (2005)