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Proceedings Paper

Characterization of the Bridgman crystal growth process by radiographic imaging
Author(s): Archibald L. Fripp; W. J. Debnam; Glenn A. Woodell; Robert F. Berry; Richard T. Simchick; S. K. Sorokach; Patrick G. Barber
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Paper Abstract

The normal characterization of a Bridgman crystal growth procedure is to note the ingot preparation, ampoule size and material, the ampoule translation rate, and the furnace zone temperatures. Even though these are important parameters which must be recorded and controlled they may not represent a sufficient set to produce repeatable growth results. One of the primary growth variables, the actual growth rate, is often ignored. Even though it is well recognized that the actual growth rate is not equal to the ampoule translation rate the difference is usually assumed small and the stochastic nature of the difference has not been previously reported. These variations between pull rate and growth rate are especially acute in unseeded growth subjected to deep supercooling. This paper discusses both elemental (Ge) and alloy (PbSnTe) crystal growth that is monitored, via radiography, to reveal both the interface position and shape in real time. Both seeded and unseeded growth are examined. The actual growth rate is shown to be a strong function of the degree of supercooling. Actual growth rates that exceed the pull rate by a factor of greater than two have been observed and the interface shape has been observed to change from concave to flat to convex during the growth.

Paper Details

Date Published: 1 December 1991
PDF: 9 pages
Proc. SPIE 1557, Crystal Growth in Space and Related Optical Diagnostics, (1 December 1991); doi: 10.1117/12.49602
Show Author Affiliations
Archibald L. Fripp, NASA/Langley Research Ctr. (United States)
W. J. Debnam, NASA/Langley Research Ctr. (United States)
Glenn A. Woodell, NASA/Langley Research Ctr. (United States)
Robert F. Berry, NASA/Langley Research Ctr. (United States)
Richard T. Simchick, Lockheed Corp. (United States)
S. K. Sorokach, Lockheed Corp. (United States)
Patrick G. Barber, Longwood College (United States)

Published in SPIE Proceedings Vol. 1557:
Crystal Growth in Space and Related Optical Diagnostics
James D. Trolinger; Ravindra B. Lal, Editor(s)

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