Erosion evolution in mono-crystalline silicon surfaces caused by acoustic cavitation bubbles

The early stages (<180 min) of cavitation erosion of silicon surfaces were studied for three different crystallographic orientations. We introduce a quantity defined as the ratio of the relative eroded area to the number of pits, αp, to evaluate the evolution of erosion among the different substrates used. Different erosion evolution was observed for (100), (110), and (111) silicon surfaces when exposed to cavitation bubbles generated by an ultrasound signal of 191 kHz. (100) silicon substrates showed the most erosion damage, with an eroded area 2.5 times higher than the other two crystallographic orientation substrates after 180 min sonication. An apparent incubation period of 50 min was measured. The number of erosion pits increased monotonically for (110) and (111), but for (100) no increase was detected after 120 min. The collapse of a spherical bubble was simulated using an axisymmetry boundary integral method. The calculated velocity of the jet from the collapsing bubble was used to estimate the pressure P that is induced by the jet upon impact on the silicon substrate.