Interplay between solution chemistry and mechanical activation in friction-induced material removal of silicon surface in aqueous solution

Shear-induced chemical etching reactions of single-crystalline Si(100), Si(110), and Si(111) surfaces were studied in acidic, neutral, and basic aqueous solutions. Measuring the applied load dependence of substrate etching yield and analyzing the data with the mechanically-assisted thermal activation model, the critical activation volume and activation barrier were determined for mechanochemical etching of three crystallographic surfaces. The pH dependence of Si(110) etching is quite distinct from those of Si(100) and Si(111). The results suggested that the mechanochemical activation effect is larger for Si(100) and Si(111) than Si(110) which is chemically more reactive than the other two surfaces. The findings of this study may provide deeper insights for mechanistic understanding of the scanning probe microscopy based nanomanufacturing and chemical mechanical polishing processes.