AVS 53rd International Symposium
    Applied Surface Science Monday Sessions
       Session AS+BI+NS+NM-MoM

Paper AS+BI+NS+NM-MoM11
Optically-Stimulated Surface Diffusion Exploited for Directed Self-Assembly on Amorphous Semiconductors

Monday, November 13, 2006, 11:20 am, Room 2005

Session: Organic Surface Modification and Nanoscale Chemical Patterning
Presenter: Y. Kondratenko, University of Illinois at Urbana-Champaign
Authors: E.G. Seebauer, University of Illinois at Urbana-Champaign
Y. Kondratenko, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
Nanoscale device fabrication technologies require toolsets for miniaturization and organization of materials at nanometer dimensions. Current toolsets have developed from two diametrically opposite strategies: top-down and bottom-up. This laboratory is taking a different approach based on a new physical mechanism for photostimulated diffusion discovered here. This new strategy combines attractive features of top-down and bottom-up approaches by exploiting the self-organization capabilities latent in amorphous materials, but in a way that can be controlled by optical or electron beam exposure tools. We have developed a new surface self-assembly method at the 10-200 nm length scale using amorphous semiconducting materials. Patterned optical or electron beam exposure yields a spatially varying surface mass flux that, when performed at an annealing temperature just at the cusp of crystallization, provides the extra nudge to crystallize subcritical nuclei in regions dictated by the light flux. The full-fledged crystallites then grow by surface diffusion and Ostwald ripening until the desired fraction of the film has accreted onto the original nuclei. We have demonstrated this technique with titanium dioxide as the substrate material. This scheme should apply to a wide variety of semiconducting materials on nearly arbitrary substrates to form nanoarrays, nanowalls, and possibly three-dimensional structures. Possible applications include chalcogenide semiconductors for data storage media; nanoparticles arrays for direct use in sensors and solar cells; and semiconductor arrays for indirect use as seed layers for the subsequent deposition of sintered particle films in fabricating advanced ceramics and devices such as rechargeable batteries, solar cells, gas sensors, and photonic band gap materials in solar windowpanes.