We have used in situ ultrahigh vacuum reflection electron microscopy to investigate the process of two-dimensional negative islands (etching pits) nucleation on extremely wide (up to 120 μm in diameter) terraces at Si(111) surface during thermal etching with molecular oxygen at temperatures above 1000 °C. By analyzing nucleation kinetics at different temperatures and comparing the results with theoretical model, we determined the dominant surface mass transport mechanism. The squared critical terrace size Dcrit2 for nucleation of new island is found to follow power law form with scaling exponent χ changing from 0.95 to 1.15 as the temperature increased Tcrit = 1180°C. At temperatures above Tcrit we estimated the energy of the vacancy-step interaction EAD as 1.5 ± 0.15 eV. We conclude that observed changes of the Dcrit in high temperature region (above Tcrit) can occur through detachment-attachment kinetics of vacancy-step exchange process rather than via surface diffusion.
- Reflection electron microscopy (REM)
- Silicon surface morphology
- Silicon-oxygen interaction
- Surface diffusion