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Science 7 July 1995:
Vol. 269. no. 5220, pp. 51 - 54
DOI: 10.1126/science.7604278
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Articles

Science, Vol 269, Issue 5220, 51-54
Copyright © 1995 by American Association for the Advancement of Science

articles

Liquid to hexatic to crystalline order in Langmuir-Blodgett films

R Viswanathan, LL Madsen, JA Zasadzinski, and DK Schwartz

Department of Chemical Engineering, University of California, Santa Barbara 93106, USA.

Atomic force microscope images of zinc arachidate (ZnA2) Langmuir-Blodgett films show that three- and five-layer films are "hexatic," with long-range bond-orientational order and short-range positional correlations of three to five lattice repeats. The monolayer in contact with the substrate is disordered. Films of seven or more layers of ZnA2 are crystalline. A population of dislocations, most likely originating at the substrate, disrupts the positional but not the orientational order of the lattice, leading to hexatic layers intermediate between crystal and liquid. The influence of the substrate propagates farther into ZnA2 films than into cadmium arachidate films because the molecular cohesion is much weaker in ZnA2 than in cadmium arachidate, as evidenced by a less dense molecular packing.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Two-Dimensional Melting of an Anisotropic Crystal Observed at the Molecular Level.
H. D. Sikes and D. K. Schwartz (1997)
Science 278, 1604-1607
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