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ECN publication
Transition-metal profiles in a multicrystalline silicon ingot
Published by: Publication date:
ECN Solar Energy 1-1-2005
ECN report number: Document type:
ECN-RX--05-060 Article (scientific)
Number of pages:

Published in: Journal of Applied Physics (American Institute of Physics), , 2005, Vol.97, p.033523-.


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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