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Research at OU


  Silicon Nanoneedles Grown by a Simple Thermal Treatment Using Metal-Sulfur Catalysts



Self-organized growth of nanostructures is of great interest in both science and technology. We found an effective method of fabricating silicon nanostructure via a self-organized process. Numerous silicon nanoneedles can be grown epitaxially on silicon substrates as shown in Figure A of a transmission electron microscopy (TEM) image. Figure B is a high-resolution TEM image of a needle. The growth direction was mostly <111>. The growth procedure was simple: silicon substrates were heated to about 1200° with metal catalyst and sulfur in an evacuated silica container. At this high temperature, sulfur makes compounds with silicon and evaporates supplying the source gas of silicon. When taken out of a furnace and cooled, gas phase silicon is captured by droplets of the metal catalyst, then supersaturated silicon in the droplets crystallizes forming silicon needles behind the droplets (Fig. C). Possible applications are field emission devices and surface texturing for optoelectronic devices. We believe that our method can be applied to the fabrication of nanostructures of other semiconducting materials.


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