Building extremely small electronic components and circuits made from individual molecules requires manipulation of the molecules into the desired arrangement. However, this remains difficult because of inconsistency in sites where molecules attach within nano-sized “circuit boards” and in the properties they exhibit in such circuits. Various research teams have sought to overcome this by studying single molecules positioned in a tiny gap between two electrodes, but obstacles to characterizing their positional and electrical features have surfaced.
A research team centered at Tokyo Tech has now precisely characterized the type of binding of a single molecule between two gold electrodes. The researchers measured the current flow when this single molecule bridged the gap between the electrodes and completed an electrical circuit, as well as the measuring the Roman scattering. Their measurements revealed the exact sites at which each end of this molecule connected with the tips of the gold electrodes, and indicated that the molecule preferentially took on three different arrangements (or bindings). This breakthrough should help to ensure site-specific binding of individual molecules used as components in nano-sized electronic circuits, making such circuits more reliable.
Recently reported in the Journal of the American Chemical Society (” Site-Selection in Single-Molecule Junction for Highly Reproducible Molecular Electronics”), this novel approach using two different analytical procedures was applied to clarify exactly how a single molecule of benzenedithiol bridged a gap of two-billionths of a meter between two gold electrodes and completed an electrical circuit. These two procedures involved measuring the current and voltage through the circuit while simultaneously analyzing the Raman scattering from a laser focused on the electrode gap. Data from over 200 of these so-called “single-molecule junctions” showed that three benzenedithiol configurations dominated, in terms of how they attached to the electrode tips, and it was possible to distinguish between them using these procedures. This novel approach can thus reveal the exact configuration of a single molecule, which enables precise construction of molecular-based circuits.