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Title:
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Transition-metal profiles in a multicrystalline silicon ingot
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-1-2005
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ECN report number:
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Document type:
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ECN-RX--05-060
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Article (scientific)
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Number of pages:
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7
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Published in: Journal of Applied Physics (American Institute of Physics), , 2005, Vol.97, p.033523-.
Abstract:
The concentrations of transition-metal impurities in a photovoltaic-grade
multicrystalline silicon
ingot have been measured by neutron activation analysis. The results
show that the concentrations
of Fe, Co, and Cu are determined by segregation from the liquid-to-solid
phase in the central regions
of the ingot. This produces high concentrations near the top of the
ingot, which subsequently diffuse
back into the ingot during cooling. The extent of this back diffusion
is shown to correlate to the
diffusivity of the impurities. Near the bottom, the concentrations are
higher again due to solid-state
diffusion from the crucible after crystallization has occurred. Measurement
of the interstitial Fe
concentration along the ingot shows that the vast majority of the Fe
is precipitated during ingot
growth. Further analysis suggests that this precipitation occurs mostly
through segregation to
extrinsic defects at high temperature rather than through solubility-limit-driven
precipitation during
ingot cooling.
Copyright (2005) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
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