Etching of step-bunched Si(1 1 1) surface by Se molecular beam observed by in situ REM

Using in situ ultrahigh vacuum reflection electron microscopy, we have first visualized the evolution of step-bunched Si(1 1 1) surface during Se beam etching depending on substrate temperature T and terrace size required for survival of etching-induced vacancies. Below T ~ 630 °C, the etching proceeds in layer-by-layer mode via periodic nucleation of small 2D vacancy islands without noticeable motion of steps. However, in 630–830 °C interval,...