Physics

Peeling away Facets

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Science  26 Oct 2001:
Vol. 294, Issue 5543, pp. 747
DOI: 10.1126/science.294.5543.747c

The stability of microcrystallites in response to changes in external conditions is an important issue in nanotechnology and microfabrication. Thürmer et al. used variable-temperature scanning tunneling microscopy to observe the transition of a lead crystallite on a ruthenium (0001) surface from one stable state to another. At temperatures between 500 and 550 K, micrometer-sized crystallites of lead are spherical. A rapid drop in temperature (to between 353 and 423 K) changes the chemical potential of the step free energy (which depends on the distances ρ and r) and leads to a shape transition that preserves volume. A (111) facet forms on top of the lead crystallite as material is transferred layer by layer to the sides of the crystallite. Sequential peeling of the top layer slows as the new stable shape is reached and the difference in chemical potential diminishes.—PDS

Phys. Rev. Lett. 10.1103/PhysRevLett.87.186102.

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