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Mechanisms controlling the hardness of Si and Ge

Published online by Cambridge University Press:  01 February 2011

L. J. Vandeperre ,
F. Giuliani ,
S. J. Lloyd  and
W. J. Clegg
L. J. Vandeperre
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom.
F. Giuliani
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom.
S. J. Lloyd
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom.
W. J. Clegg
Affiliation:
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, United Kingdom.
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Abstract

It is generally accepted that the hardness of silicon and germanium is limited by a phase transformation. Observations of the deformation under indents using transmission electron microscopy indicate that, in addition to the phase transformation, there is also plastic flow both in the transformed and in the untransformed material. These observations are consistent with those made elsewhere and with predictions based on the spherical cavity model for indentation, modified to quantify the effect of a phase transformation on the measured hardness. The analysis predicts that the hardness can only be approximately equal to the transformation pressure provided the yield strength of the transformed material is low, and that there is a region where plastic deformation in the untransformed material can occur in addition to the phase transformation. These predictions are consistent with the experimental observations of substantial plastic deformation of the transformed phase, as well as with estimates of its Peierls stress.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 795: Symposium U – Thin Films - Stresses and Mechanical Properties X , 2003 , U8.22
Copyright
Copyright © Materials Research Society 2004

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References

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