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Inert gases in closed crystal growth systems

Witold Palosz

Universities' Space Research Association/NASA Marshall Space Flight Ctr. (USA)

The effect of desorption from, and diffusion through the wall on inert gas pressure in sealed fused silica ampoules was investigated. It is shown, that desorption from the surface and the bulk of silica may lead to an accumulation of residual gas on the order of a few Torr or more upon annealing. A prior outgassing of the ampoules under vacuum at high temperature reduces the amount of gas released from the glass by at least one order of magnitude. Presence of oxide and other impurities in the source material was found to increase the residual gas pressure, affect its composition, and reduce the vapor transport rate in PVT systems. It is shown, that light gases (hydrogen, helium, and neon) diffuse through silica wall and may change the pressure inside the sealed ampoule considerably even at moderate temperatures.

©2004 COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

doi:10.1117/12.277733
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