Nanoindentation-Induced Phase Transformation in Silicon

TL;DR

This study investigates how nanoindentation induces phase transformations in silicon, revealing conditions that favor crystalline or amorphous phases through Raman spectroscopy and TEM analysis.

Contribution

It demonstrates the specific load conditions that promote high-pressure crystalline phases in silicon during nanoindentation, with detailed microscopic characterization.

Findings

High-pressure phases appear at loads up to 3000 μN.

Optimal crystalline phase transformation occurs at 5000 μN load.

Phase transformations can occur without visible pop-in or pop-out signals.

Abstract

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.