  Nanoindentation-induced phase transformation in silicon has been studied. A
series of nanoindentations were made with the sharp diamond Berkovich tip.
During nanoindentations, maximum load ranged from 2000 $\mu$N to 5000 $\mu$N,
with a 1000 $\mu$N/sec loading rate. Slow unloading rate at 100$\mu$N/sec was
chosen to favor the formation of the crystalline end phases, high pressure
phase (Si-III and Si-XII). Fast unloading rate at 1000$\mu$N/sec was used to
obtain amorphous phase. The phase transformation was examined by Raman
spectroscopy and plan-view transmission electron microscopy (TEM). HPP have
been identified even if no "pop-in" and "pop-out" observed in load-depth
characteristics curves. HPP appeared in c-Si when the maximum load up to 3000
$\mu$N. TEM images have been revealed that the optimization HPP transformation
in c-Si at the nanoscale occurred when the maximum load applied at 5000 $\mu$N.
