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Science 28 November 1997:
Vol. 278. no. 5343, pp. 1604 - 1607
DOI: 10.1126/science.278.5343.1604
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Reports
Two-Dimensional Melting of an Anisotropic Crystal Observed at the Molecular Level
H. D. Sikes,
D. K. Schwartz
*
A distinctive two-dimensional (2D) melting transition occurring at
nearly 100 degrees Celsius (°C) has been observed in
Langmuir-Blodgett films by in situ atomic force microscopy (AFM). A 2D
orthorhombic crystal phase melted to a 2D smectic phase at about
91°C. The smectic phase was characterized by 1D molecular periodicity
with short-range correlations (about 40 angstroms). At 95°C, the
smectic order melted to form a hexatic phase. Infrared spectroscopy
measurements were consistent with the AFM observations. These
observations support the dislocation-mediated melting scenario for an
anisotropic 2D crystal predicted by Ostlund and Halperin. A longer
wavelength height modulation was also observed in the smectic and
hexatic phases.
Department of Chemistry, Tulane University, New Orleans, LA 70118, USA.
*
To whom correspondence should be addressed.
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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
- Multiple-Step Melting in Two-Dimensional Hexatic Liquid-Crystal Films.
- C. Chou, A. J. Jin, S. W. Hui, C. C. Huang, and J. T. Ho (1998)
Science
280, 1424-1426
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