Quantum dots breakthrough
Sep 3, 1999
Efforts to develop new electronic devices based on quantum dots could benefit from a new approach developed by physicists in Germany. Stefan Facsko and colleagues from RWTH Aachen and the Technical University of Darmstadt in Germany have produced a hexagonal array of dots by bombarding a gallium antimonide surface with argon ions (Science 285 1551). The dots had diameters of 35 nanometres and "self-organized" into the hexagonal pattern.
Only two other methods have previously been used to manufacture quantum dots: electron beam lithography and epitaxy. Lithography is a top down approach in which the beam defines the dot pattern, whereas epitaxy is a bottom-up approach in which the dots self-organize. Ion bombardment or sputtering is more cost effective and easily controllable than the other two techniques.
The latest approach relies on the "tug-of-war" between the sputtering, which roughens the gallium antimonide surface, and surface tension, which smoothes the surface. It only takes between 200 and 400 seconds for the quantum dots to form. Possible applications include photovoltaics, semiconductor lasers and protein tagging.