Abstract
The formation of copper atomic contacts has been investigated. Copper nanowires were grown by electrochemical deposition, in the scanning electrochemical microscopy (SECM) configuration, from a platinum microelectrode to an indium tin oxide (ITO) substrate. Self-termination leaves copper filaments between the two electrodes with an atomic point contact at the ITO electrode. Histogram analysis shows that the conductance of this contact is close to, or less than, 1 G0. Atomic contacts were also fabricated on ITO electrodes covered with vertically-aligned mesoporous silica films. Scanning Transmission Electron Microscopy images show that copper filaments occupy individual isolated nanopores. Contacts generated on bare ITO break down rapidly in sodium salicylate, whereas those generated in ITO/nanopores are unaffected; the nanopores protect the copper filaments. Finally, atomic switch behaviour was obtained using these ITO and ITO/nanopores electrodes.
Highlights
For several metals it is close to unity at room temperature[18,19]
The fact that the nanowire conductance depends neither on the length or the tip radius establishes that transport is not governed by a classical regime (Ohm’s Law)
In order to see whether the mesoporous silica film could protect the Cu atomic contact, we studied the effect of sodium salicylate on Cu nanowire conductance
Summary
For several metals (gold, copper, silver) it is close to unity at room temperature[18,19]. Atomic contacts were generated by using another type of ITO electrode, which was covered with a highly ordered mesoporous silica thin film with a vertical alignment of small pore channels Such films, consisting of closely packed hexagonal nanopores, can be generated on ITO by electro-assisted self-assembly[44,45]. These substrates have perfect molecular sieving properties[46], can be functionalized with organic groups[47], and are promising hard templates for nano-casting[48,49]. The nanopores after Cu growth are imaged by high-resolution electron micrographs; protection by the nanopores and atomic switch behavior were studied
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