Nanofabrication using scanned-probe technology including the scanning tunneling microscope and the atomic force microscope offers a unique combination of capabilities that include the potential for the ultimate atomic-scale control of matter and for high-speed patterning by operating multiple probes in parallel. One of the most promising and widely investigated techniques for scanned-probe nanofabrication is the surface oxidation of Si. This process uses a probe tip to locally oxidize a H-passivated Si surface. The oxidation is performed either in air by using an electrochemical reaction involving the tip, sample and ambient humidity or in vacuum by direct atomic-level depassivation of the surface and subsequent exposure to oxygen. Because of the contrasting chemistry of the H-passivated Si and the patterned SiO2 regions, this local oxidation process has found many applications including writing of the oxide for use as a template for the selective attachment of molecular monolayers, for use as an etch mask, and for fabricating both semiconductor and metallic nanodevices. In this presentation we report on important new developments in the science and technology of scanned probe oxidation. These developments include a new model that explains the rate limiting kinetics of the oxidation process and a fast, reliable method for fabricating metal silicide nanostructures and lateral silicide/Si/silicide tunnel junctions. We report extremely high effective write speeds approaching 10 cm/s for the oxidation and silicide processes. When combined with newly developed parallel probe technology such high write speeds make scanned probe technology an attractive tool for high-throughput nanofabrication of conventional structures as well as more exotic techniques such as the fabrication of templates for directed self assembly.
Head, Nanostructures Section, Code 6876, Naval Research Laboratory
Washington, DC 20375
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