Oxygen effects on the Vickers hardness of silicon: a statistical and mechanistic study

Hardness is a critical mechanical property that directly influences the processing and surface quality of silicon wafers. This work systematically investigates the effects of interstitial oxygen atoms and oxygen precipitates on the room-temperature Vickers hardness of silicon. We first establish a statistically rigorous methodology for hardness testing, demonstrating that a minimum sample size of 40 is required to obtain reliable and stable results. Based on this robust approach, independent samples t-tests and effect size analysis definitively show that neither the interstitial oxygen atoms nor the oxygen precipitates exert a statistically or practically significant effect on the hardness. Most importantly, we delve beyond macroscopic properties to uncover the underlying physical mechanism. Statistical analysis of Raman spectra on 40 indentations, combined with transmission electron microscopy microstructural analysis, reveals that the invariance of hardness stems from the fact that neither the interstitial oxygen atoms nor the oxygen precipitates alter the final products of the indentation-induced phase transformation. This work not only resolves a scientific debate but also provides a mechanistic understanding crucial for the precise evaluation of mechanical properties of silicon.