Page "Molecular electronics" Paragraph 8

One of the biggest problems with measuring on single molecules is to establish reproducible electrical contact with only one molecule and doing so without shortcutting the electrodes.

Because the current photolithographic technology is unable to produce electrode gaps small enough to contact both ends of the molecules tested ( in the order of nanometers ) alternative strategies are put into use.

These include molecular-sized gaps called break junctions, in which a thin electrode is stretched until it breaks.

Another method is to use the tip of a scanning tunneling microscope ( STM ) to contact molecules adhered at the other end to a metal substrate.

Another popular way to anchor molecules to the electrodes is to make use of sulfur's high affinity to gold ; though useful, the anchoring is non-specific and thus anchors the molecules randomly to all gold surfaces, and the contact resistance is highly dependent on the precise atomic geometry around the site of anchoring and thereby inherently compromises the reproducibility of the connection.

To circumvent the latter issue, experiments has shown that fullerenes could be a good candidate for use instead of sulfur because of the large conjugated π-system that can electrically contact many more atoms at once than a single atom of sulfur.