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Measurement of Temperature Fluctuations and Microscopic Growth Rates in a Silicon Floating Zone on TEXUS36Several pg experiments on sounding rockets and the Space Shuttle have shown that time-dependent thermocapillary (Marangoni) convection is the major cause for the formation of dopant striations in floating-zone grown semiconductor crystals, at least in small-scale systems not employing RF heating. To quantify this correlation, a silicon floating-zone experiment was performed during the TEXUS36 flight (February 7, 1 998) in the monoellipsoid mirror furnace TEM02-ELLI. During the experiment, temperature fluctuations in the silicon melt zone and the microscopic growth rate were simultaneously measured. Temperature fluctuations of 0.5 C - 0.7 C with main frequencies between 0.1 Hz and 0.3Hz were detectable. The microscopic growth rate fluctuated considerably around the average growth rate of 1 mm/min: rates from 4mm/min to negative values (backmelting) were observed. Dopant striations are clearly visible in the Sb-doped crystal. They were characterized by Spreading Resistance measurements and Differential Interference Contrast microscopy. The frequencies associated with the dopant inhomogeneities correspond quite well with those of the temperature fluctuations and microscopic growth rates. 3D numerical simulations were performed to predict the optimum position of the temperature sensor, to evaluate characteristic temperature amplitudes and frequencies, and to give insight into the instability mechanisms of Marangoni convection in this configuration. The simulations were in good agreement with the experimental values, showing temperature fluctuations with frequencies? 0.25 Hz and amplitudes up to 1.8 C at a position equivalent to that of the sensor tip in the experiment.
Document ID
19990109090
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Croell, Arne
(NASA Marshall Space Flight Center Huntsville, AL United States)
Schweizer, Markus
(NASA Marshall Space Flight Center Huntsville, AL United States)
Dold, P.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Kaiser, Th.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Lichtensteiger, M.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Benz, K. W.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Solid-State Physics
Meeting Information
Meeting: European Space Components
Location: Noordwijk
Country: Netherlands
Start Date: March 20, 2000
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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