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Metastability of Au-Ge liquid nanocatalysts: Ge vapor-liquid-solid nanowire growth far below the bulk eutectic temperature

Adhikari, Hemant and Marshall, Ann F. and Goldthorpe, Irene A. and Chidsey, Christopher E. D. and McIntyre, Paul C. (2007) Metastability of Au-Ge liquid nanocatalysts: Ge vapor-liquid-solid nanowire growth far below the bulk eutectic temperature. ACS NANO, 1 (5). pp. 415-422.

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Official URL: http://dx.doi.org/10.1021/nn7001486

Abstract

The vapor-liquid-solid mechanism of nanowire (NW) growth requires the presence of a liquid at one end of the wire; however, Au-catalyzed Ge nanowire growth by chemical vapor deposition can occur at similar to 100 degrees C below the bulk Au-Ge eutectic. In this paper, we investigate deep sub-eutectic stability of liquid Au-Ge catalysts on Ge NWs quantitatively, both theoretically and experimentally. We construct a binary Au-Ge phase diagram that is valid at the nanoscale and show that equilibrium arguments, based on capillarity, are inconsistent with stabilization of Au-Ge liquid at deep sub-eutectic temperatures, similar to those used in Ge NW growth. Hot-stage electron microscopy and X-ray diffraction are used to test the predictions of nanoscale phase equilibria. In addition to Ge supersaturation of the Au-Ge liquid droplet, which has recently been invoked as an explanation for deep sub-eutectic Ge NW growth, we find evidence of a substantial kinetic barrier to Au solidification during cooling below the nanoscale Au-Ge eutectic temperature.

Item Type:Article
Uncontrolled Keywords:sub-eutectic growth; phase diagram; nanowires; germanium; nanocatalyst; TEM; Au-Ge
Subjects:Material Science > Nanochemistry
Material Science > Nanostructured materials
ID Code:2363
Deposited By:Anuj Seth
Deposited On:17 Dec 2008 15:38
Last Modified:17 Dec 2008 15:38

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