Crystalline silicon under acoustic cavitation: From mechanoluminescence to amorphization

The physicochemical behavior of crystalline silicon under acoustic cavitation is investigated in water sparged with argon at low temperature (10 and 20 °C). Surprisingly, spectroscopic investigations reveal that argon (bubbling continuously through the liquid phase during experiments) can be ultrasonically excited via mechanoluminescence, i.e., emission of light caused by mechanical action on a solid. This phenomenon is highlighted for the first time on an extended solid surface using these conditions and results from an interaction between the acoustically generated bubbles and the Si surface. The concomitant physical and chemical transformations induced at the solid–liquid interface are investigated (SEM, AFM) to characterize the generated stress and defects in combination with the roughness and wettability increases (evolving from ∼46° to ∼4°). Phase transformations of the Si lattice are observed (Raman spectroscopy, TEM) evidencing the complex stress state induced by acoustic cavitation in the Si crys...