Transport phenomena and crystal growth of the GeSe-Xenon system for different gravitational conditions |
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Authors: | H. Wiedemeier R.C. Whiteside |
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Affiliation: | Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York, NY 12181, USA |
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Abstract: | Previous chemical vapor transport experiments of the GeSe-GeI4 system performed under reduced gravity conditions /1/ yielded crystals of considerably improved surface and bulk morphology. In addition, the mass transport rates observed in microgravity environment were significantly greater than predicted. A quantitative thermodynamic analysis of the solid-gas phase reactions of the GeSe-GeI4 system revealed the multi-component, multi-reaction nature of the vapor phase /2/. Continued transport studies on ground of the GeSe-GeI4 system in the presence of inert gases provided experimental evidence for the existence of a boundary layer /2/ and its thickness dependence on GeI4 pressure in closed tube systems. Systematic transport rate measurements for different orientations of the density gradient relative to the gravity vector demonstrated the effects of ampoule inclination on mass flux /3/. Based on a computational model for simultaneous chemical vapor transport, sublimation, and Stefan flow /3/, the excellent agreement of predicted with ground-based experimental mass transport rates over wide pressure ranges /3/ confirmed the validity of the model and the discrepancy between observed and expected transport rates of the GeSe-GeI4 system in microgravity. |
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