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Department of Materials Science & Engineering Northwestern University November 3, 2004
Nanowires offer great potential in a wide range of applications from nanoelectronics to chemical sensors. The conditions for wire growth at the nanoscale by the VLS process are considerably different from those governing the micron size wires grown many years ago by Wagner. Capillary effects become more important and the conditions governing the stability of the solid-liquid interface are altered. Motivated by insitu electron microscopy images of the later stages of wire growth, we have examined the effects of capillarity on the growth rate of a wire, the composition of the liquid droplet and the evaporation rate of the liquid into the surrounding atmosphere. Using this information we examine the conditions governing the existence of the liquid gold catalyst during Si-wire growth. The planarity of the solid-liquid interface is extremely important to insure that the composition of the resulting solid is uniform. We examine the morphological stability of the growing solid-liquid interface during VLS growth. We find that for many systems the diameter of the wire is less than the critical wavelength for the onset of morphological instability, implying that the solid-liquid interface should remain planar without the presence of faceting. |
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