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Science 19 September 2008:
Vol. 321. no. 5896, pp. 1660 - 1664
DOI: 10.1126/science.1162049

Reports

4D Electron Diffraction Reveals Correlated Unidirectional Behavior in Zinc Oxide Nanowires

Ding-Shyue Yang, Changshi Lao, Ahmed H. Zewail*

The confined electronic structure of nanoscale materials has increasingly been shown to induce behavior quite distinct from that of bulk analogs. Direct atomic-scale visualization of nanowires of zinc oxide was achieved through their unique pancake-type diffraction by using four-dimensional (4D) ultrafast electron crystallography. After electronic excitation of this wide-gap photonic material, the wires were found to exhibit colossal expansions, two orders of magnitude higher than that expected at thermal equilibrium; the expansion is highly anisotropic, a quasi–one-dimensional behavior, and is facilitated by the induced antibonding character. By reducing the density of nanowires, the expansions reach even larger values and occur at shorter times, suggesting a decrease of the structural constraint in transient atomic motions. This unanticipated ultrafast carrier-driven expansion highlights the optoelectronic consequences of nanoscale morphologies.

Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.

* To whom correspondence should be addressed. E-mail: Zewail{at}caltech.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Ordered water structure at hydrophobic graphite interfaces observed by 4D, ultrafast electron crystallography.
D.-S. Yang and A. H. Zewail (2009)
PNAS 106, 4122-4126
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Science. ISSN 0036-8075 (print), 1095-9203 (online)