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The Influence of Static and Rotating Magnetic Fields on Heat and Mass Transfer in Silicon Floating ZonesHeat and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio-frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a defined flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to 5 T and in transverse rotating magnetic fields up to 7.5 mT. Static fields of a few 100 mT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile toward a more diffusion-limited case, is possible with static fields greater than or equal to 1 T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelectromagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few millitesla. The field shifts time- dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes.
Document ID
20000012412
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Croll, A.
(Alabama Univ. Huntsville, AL United States)
Dold, P.
(Freiburg Univ. Germany)
Kaiser, Th.
(Freiburg Univ. Germany)
Szofran, F. R.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Benz, K. W.
(Freiburg Univ. Germany)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Journal of the Electrochemical Society
Publisher: Electrochemical Society
Volume: 146
ISSN: 0013-4651
Subject Category
Nonmetallic Materials
Funding Number(s)
CONTRACT_GRANT: DLR-50QV8956
CONTRACT_GRANT: DLR-50WM9505
CONTRACT_GRANT: DLR-50WM9503
Distribution Limits
Public
Copyright
Other

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