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Engineering

  Formation of Nanowires along Ion Trajectories in Si Backbone Polymers

 

 

High density energy deposition by ion beams causes non-homogeneous crosslinking reaction of polysilane derivatives within a nano-sized cylindrical area along an ion trajectory, and gives β-SiC based nano-wires of which sizes (length, thickness) and number densities are completely under control by changing the parameters of incident ion beams and molecular sizes of target polymers. A 3-D AFM image of nano-wires adhered on a Si substrate is displayed as yellow tones in the figure. Superimposed top-view picture shows the piled-up nanowires of which number density per area completely reflects the number of incident ions in this area. SEM images indicate the aggregated nanowires which are observed on the Si substrate without an adequate surface treatment. It is clear that the nano-wire is no longer isolated in this case, and entangled each other. The aggregated nano-wires are rarely and randomly distributed on the substrate, and the majority is washed out together with uncross-linked parts of the film. Our results also show that the spatial distribution and size of the isolated nanowires can be fairly controlled by this technique unlike those for producing carbon nanotubes or wires. The radius of the wire varies from a few nm to 15 nm, and is precisely controlled by simply changing the parameters of incident ion beam or molecular weights of the target polymer. The thickness of the target film determines the length of each wire, which is also under control by the present technique.  

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