Atomic configuration, conductance, and tensile force of platinum wires of single-atom width

Platinum (Pt) wires of single-atom width were produced by the retraction of a Pt nanotip from contact with a Pt plate at room temperature inside a transmission electron microscope. The distance between the nanotip and the plate was controlled using a conductance feedback system, as a result of which wires showing certain conductance values were observed continuously by in situ lattice imaging. Simultaneously, the force acting on the wires was measured using a function of atomic force microscopy. The tip-plate distance was also increased with a constant speed, and the atomic configuration, force, and conductance were similarly investigated. The single-atom-width Pt wires were found to exhibit straight shapes with an interatomic distance of 0.28±0.03 nm. The wires were stable at a tensile force of approximately 1 nN; the observed interatomic distance resulted from elastic expansion. The present study demonstrated experimental evidence for the relationship between wire length and conductance; the wires extend from a three-atom length to a five-atom length as the selected feedback conductance decreases from 2.0 to 0.5G0 (where G0=2e2/h, e being the charge of an electron and h Planck’s constant). Contacts exhibiting a conductance of 3.0G0 were two-atom-width contacts. In a conductance histogram constructed from the simple retraction, only one peak was observed at 1.3G0. Thus, it was found that the conductance of single-atom-width Pt wires is less than 3.0G0, with 1.3G0 being that of the most-stable state