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6 July 1999 Influence of applied thermal gradients and a static magnetic field on Bridgman-grown GeSi alloys
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The effect of applied axial and radial thermal gradients and an axial static magnetic field on the macrosegregation profiles of Bridgman-grown GeSi alloy crystals has been assessed. The axial thermal gradients were adjusted by changing the control setpoints of a seven-zone vertical Bridgman furnace. The radial thermal gradients were affected by growing samples in ampoules with different thermal conductivities, namely graphite, hot-pressed boron nitride (BN), and pyrolytic boron nitride (PBN). Axial macrosegregation profiles of these samples fell between the predictions for a completely mixed melt and one where solute transport is dominated by diffusion. All of the samples were grown on Ge seeds. This resulted in a period of free grown until the Si concentration in the solid was in equilibrium with the Si concentration in the liquid. The length of crystal gown during this period was inversely proportional to the applied axial thermal gradient. Several samples were grown in an axial 5 Tesla magnetic field. Measured macroscopic segregation profiles on these samples indicate that the magnetic field did not, in general, reduce the melt flow velocities to below the growth velocities.
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Martin P. Volz, Frank R. Szofran, Sharon D. Cobb, and Timothy M. Ritter "Influence of applied thermal gradients and a static magnetic field on Bridgman-grown GeSi alloys", Proc. SPIE 3792, Materials Research in Low Gravity II, (6 July 1999);

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