AARHUS, DenmarkResearchers at Aarhus University here have demonstrated a nanometer-scale fabrication technique that self-assembles tiny wires atop substrates, with an eye toward interconnecting molecular electronic circuits in the future.
The team demonstrated how a template molecule could form wires measuring only 2 atoms wide atop a copper substrate, said Flemming Besenbacher, director of the university's Nanoscience Center, who conducted the work with researchers Federico Rosei and Michael Schunackm. "Our self-fabrication process makes use of the shape of a template molecule at the nanoscale to enable interconnecting molecules with atomic-scale precision," said Besenbacher.
A French team led by researcher Christian Joachim at CEMES-CNRS (Toulouse Cedex, France) provided the theoretical underpinning for the Besenbacher team's work. The theory indicated that a template molecule could enable the self-fabrication of metallic nanostructures at step edges by reshaping the molecules "under" the template.
The template was an organic molecule (C90H98) in the shape of a "table," i.e., the "top" of the table is separated from the substrate on which it sits by four "legs." By setting the template down on the step edge, the researchers established conditions under which 16 copper molecules, arranged two wide by eight long, were trapped underneath the table and lifted off the substrate, forming a metallic wire measuring only 0.75 nanometer wide by 1.85 nanometers long.
Next up: self-assembly
The molecular templates theorized by Joachim were realized here by first supercooling the materials, to slow their atomic vibrations, and then manipulating their individual atoms with a scanning-tunneling microscope (STM). Once the template molecule and its actions are perfected using the STM, the researchers hope to develop self-assembly techniques that do not require human manipulation with an STM.
European researchers prefer a "bottom-up" approach to building molecular-size electronic devices that is, self-assembling individual molecules rather than the traditional "top-down" approach inherent in traditional lithography techniques, Besenbacher said. The European researchers hope to fill their nanotool kits with prefabricated molecular building blocks that can be coaxed to self-assemble into desirable nanoscale circuitry.