Contact resistance and phase transformations during nanoindentation of silicon

A. B. Mann, D. Van Heerden, J. B. Pethica, P. Bowes, T. P. Weihs

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An electrically conductive VC tip has been used in conjunction with ex-situ transmission electron microscopy (TEM) and micro-Raman spectroscopy to examine the behaviour of silicon during nanoindentation testing. During loading, the contact resistance is low because of the presence of the metallic P-Sn phase of silicon. During unloading, the semimetallic BC8 phase and the rhombohedral R8 phase are formed, giving rise to an increase in the contact resistance. In large indentations there is a pronounced discontinuity in both the contact resistance-depth and load-depth curves during unloading. This signifies the formation of a phase with lower electrical resistance. TEM analysis suggests that this phase is amorphous silicon formed in the centre of large indentations. The position of the discontinuity on the load-depth curve is found to depend on the unloading rate, as would be expected for the generation of an amorphous phase. Micro-Raman analysis is largely in agreement with the TEM results, but the amorphous silicon is seen most clearly when there are cracks present, suggesting that the amorphous phase may be subsurface or generated during the rapid propagation of cracks.

Original languageEnglish (US)
Pages (from-to)1922-1929
Number of pages8
JournalPhilosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties
Issue number10
StatePublished - Jul 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Materials Science(all)
  • Condensed Matter Physics
  • Physics and Astronomy (miscellaneous)
  • Metals and Alloys


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