SI OVERGROWTH ON SI(111)ROOT-3X-ROOT-3-B SURFACE PHASE

Si(111)root 3 X root 3-B surface phase has been formed by high-tempera ture annealing of B-doped Si samples. Low-energy electron diffraction observations have revealed that the Si(111)root 3 X root 3-B surface p hase is very stable with respect to heating and that the root 3 X root 3 reconstruction is still detected at temperature as high as 950 degr ees C. Scanning tunnelling microscopy has been used to study the growt h of Si on Si(111)root 3 x root 3-B surface. At low temperatures (20-3 00 degrees C) the growth has been found to be affected greatly by surf ace defects which trap Si atoms and act as sites of preferential islan d nucleation. At temperatures of Si(111) epitaxy (greater than or equa l to 400 degrees C) Si islands grow amorphous up to a certain critical size and then ''crystallize'' to form epitaxial islands with a thickn ess of two Si(111) bilayers. The structure on top of epitaxial Si isla nds is always root 3 X root 3 which suggests boron segregation to the surface.