Atomic Arrangement and Conductance of Metal Nanowires

Abstract

We have used high resolution transmission electron microscopy and mechanically controllable break junction technique to study metal NW structure and electrical transport properties. In the last stages just before rupture, gold and platinum nanowires are crystalline and defect-free. In particular, gold NWs assume merely three kinds of atomic arrangements, which were correlated to observed conductance behaviors.Introduction The interest in nanometric systems has grown because they show intriguing new effects, which can be used to study quantum phenomena and to generate novel electronic devices. One of these systems is the metal nanowire (NW), which has attracted great attention due to its quantized conductance. NWs can be obtained in a simple way by putting in contact two clean metal surfaces and subsequently separating them; NWs are generated during the contact breaking. Just before rupture, conductance measurements display flat plateaus connected by abrupt jumps whose value is approximately a conductance quantum G 0 ¼ 2e 2 =h (where e is the electron charge and h is Planck's constant) [1]. In this kind of experiment, each new measurement corresponds to a different metal NW and conductance curves show dissimilar profiles [2], raising the question about the role of structural and electronic effects on the conductance changes.In this work, we have analyzed gold and platinum NWs generated by mechanical elongation, using a high resolution transmission electron microscope. We have observed that, just before rupture, metal NWs are crystalline and defect-free. Also, for gold, we reduced the number of possible NW atomic configuration to only three cases. Using a simple geometrical model we have estimated the conductance behavior for each NW type and its occurrence probabilities, that showed a remarkable agreement with experimental data measured with a mechanically controllable break junction.

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