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Evaluating Amorphization Around Micro-Cracks in PV Silicon

Published online by Cambridge University Press:  31 January 2011

Prashant K. Kulshreshtha
Affiliation:
[email protected], North Carolina State University, Materials Science and Engineering, Raleigh, North Carolina, United States
Khaled M. Youssef
Affiliation:
[email protected], North Carolina State University, Materials Science and Engineering, Raleigh, North Carolina, United States
George Rozgonyi
Affiliation:
[email protected], North Carolina State University, Materials Science and Engineering, Raleigh, North Carolina, United States
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Abstract

Since the initiation and propagation of a micro-crack in a silicon wafer introduces local variations in stress, it is critical to the understanding of wafer breakage that accurate profiling of stress be performed in the vicinity of the micro-crack. In this study, nanoindentation has been used to investigate the stress-relaxation during crack initiation and propagation in material of particular interest to the photovoltaic (PV) industry. The low load (<1 mN) capability of a Hysitron Triboindenter® was used to accurately profile the extent of plastic deformation and resulting amorphization. Measurements were made on Si samples extracted from top, middle and bottom of a (100) oriented single crystal ingot to evaluate the impact of different carbon, oxygen and metallic impurity concentrations. A gradual but significant drop in hardness from 10.2 to 6.9 GPa occurred as indents were made closer to the micro-crack and was attributed to local amorphization. Electron back scattered diffraction (EBSD) and Raman spectroscopy confirmed the amorphization, respectively, at nano- and micro-scale.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

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