Recent developments in techniques of real space observations of surfaces are notable. In them reflection electron microscopy (REM) is a unique technique where in-situ real time observations of wide areas of surfaces are possible. In the present paper recent studies of surface dynamic processes on Si surfaces are reviewed. Observed dynamic processes are adsorption induced successive phase transitions, adsorbate induced facet formations and step rearrangements induced by a reversal of specimen heating current direction(so called current effect) and by a reversal of the sign of the surface strain(strain effects).

Figure 1 reproduces a series of REM images and RHEED patterns taken during successive phase transition induced by Au deposition on a clean Si(lll) surface at 780°C[l]. (a) shows a REM image taken before Au deposition. Line images with zigzag in shape are atomic steps on the surface. The surface steps up to the right as indicated by a step mark. The corresponding RHEED pattern in (b) shows that the surface has the 7×7 structure.