Abstract
The mixture of the metastable body-centered cubic (bc8) and rhombohedral (r8) phases of silicon
that is formed via nanoindentation of diamond cubic (dc) silicon exhibits properties that are of
scientifc and technological interest. This letter demonstrates that large regions of this mixed phase
can be formed in crystalline Si via nanoindentation without signifcant damage to the surrounding
crystal. Cross-sectional transmission electron microscopy is used to show that volumes 6 um wide
and up to 650 nm deep can be generated in this way using a spherical tip of 21.5 um diameter. The
phase transformed region is characterised using both Raman microspectroscopy and transmission
electron microscopy. It is found that uniform loading using large spherical indenters can favor
phase transformation as the sole deformation mechanism as long as the maximum load is below a
critical level. We suggest that the sluggish nature of the transformation from the dc-Si phase to
the metallic (b-Sn) phase normally results in competing deformation mechanisms such as slip and
cracking but these can be suppressed by controlled loading conditions.
