Observation of the morphology of thin films of solid helium deposited from the fluid onto sapphire

Thin layers of solid helium were grown on sapphire single-crystal substrates at pressures from about 500 bar to 9 kbar. Grain boundaries can be observed in these layer crystals. The morphology of the grains depends on the crystal modification. In the hcp phase (below about 1.13 kbar) a system of par...

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Bibliographic Details
Published in:Journal of low temperature physics 1985, Vol.58 (1-2), p.153-170
Main Authors: FRANCK, J. P, GLEESON, J, KORNELSEN, K. E, MANUEL, J. R, MCGREER, K. A
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
Films (including physical adsorption)
Physics
Quantum fluids and solids
liquid and solid helium
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Summary:Thin layers of solid helium were grown on sapphire single-crystal substrates at pressures from about 500 bar to 9 kbar. Grain boundaries can be observed in these layer crystals. The morphology of the grains depends on the crystal modification. In the hcp phase (below about 1.13 kbar) a system of parallel bands is observed, probably due to slip and twinning. In the fcc phase (above 1.13 kbar) a polygonal structure similar to a helium froth is found. Melting of this froth in the fcc phase shows grain boundary melting; fluid helium is wetting the fcc grains. Grain boundaries in the hcp phase are, in contrast, not wetted by fluid helium.
ISSN:0022-2291
1573-7357
DOI:10.1007/BF00682571