Engineering the growth of germanium nanowires by tuning the supersaturation of Au/Ge binary alloy catalysts
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Accepted Version
Date
2013-07-08
Authors
O'Regan, Colm
Biswas, Subhajit
O'Kelly, Curtis
Jung, Soon Jung
Boland, John J.
Petkov, Nikolay
Holmes, Justin D.
Journal Title
Journal ISSN
Volume Title
Publisher
American Chemical Society
Published Version
Abstract
The synthesis of Ge nanowires with very high-aspect ratios (greater than 1000) and uniform crystal growth directions is highly desirable, not only for investigating the fundamental properties of nanoscale materials but also for fabricating integrated functional nanodevices. In this article, we present a unique approach for manipulating the supersaturation, and thus the growth kinetics, of Ge nanowires using Au/Ge bilayer films. Ge nanowires were synthesized on substrates consisting of two parts: a Au film on one-half of a Si substrate and a Au/Ge bilayer film on the other half of the substrate. Upon annealing the substrate, Au and Au/Ge binary alloy catalysts were formed on both the Au and Au/Ge-sides of the substrates, respectively, under identical conditions. The mean lengths of Ge nanowires produced were found to be significantly longer on the Au/Ge bilayer side of the substrate compared to the Au-coated side, as a result of a reduced incubation time for nucleation on the bilayer side. The mean length and growth rate on the bilayer side (with a 1 nm Ge film) was found to be 5.5 ± 2.3 μm and 3.7 × 10–3 μm s–1, respectively, and 2.7 ± 0.8 μm and 1.8 × 10–3 μm s–1 for the Au film. Additionally, the lengths and growth rates of the nanowires further increased as the thickness of the Ge layer in the Au/Ge bilayer was increased. In-situ TEM experiments were performed to probe the kinetics of Ge nanowire growth from the Au/Ge bilayer substrates. Diffraction contrast during in situ heating of the bilayer films clarified the fact that thinner Ge films, that is, lower Ge concentration, take longer to alloy with Au than thicker films. Phase separation was also more significant for thicker Ge films upon cooling. The use of binary alloy catalyst particles, instead of the more commonly used elementary metal catalyst, enabled the supersaturation of Ge during nanowire growth to be readily tailored, offering a unique approach to producing very long high aspect ratio nanowires.
Description
Keywords
Nanowires , Germanium , Supersaturation , Growth rate , Vapor-liquid-solid growth , Semiconductor nanowires , Nanoelectromechanical devices , Silicon nanowires , Phase diagram , Ge nanowires , Temperature , Nucleation , Au , Anodes
Citation
O’REGAN, C., BISWAS, S., O’KELLY, C., JUNG, S. J., BOLAND, J. J., PETKOV, N. & HOLMES, J. D. 2013. Engineering the Growth of Germanium Nanowires by Tuning the Supersaturation of Au/Ge Binary Alloy Catalysts. Chemistry of Materials, 25, 3096-3104. http://dx.doi.org/10.1021/cm401281y
Copyright
© 2013 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/cm401281y