SURFACTANT EPITAXY OF SI ON SI(111) SURFACE MEDIATED BY A SN LAYER .1. REFLECTION ELECTRON-MICROSCOPE OBSERVATION OF THE GROWTH WITH AND WITHOUT A SN LAYER MEDIATE THE STEP FLOW

Surfactant epitaxy of Si on Si(111)7 x 7 surface is studied by high-resolution reflection electron microscopy with and without a Sn layer which promotes the step flow growth. The Si adatoms deposited on the Sn layer forming the square-root 3 x square-root 3 structure are found to be incorporated with the bulk Si layer, so that the surface is covered always by the Sn layer and the growth proceeds by the step flow. The critical step distance above which islands nucleate on the terraces is determined for the growths of Si/Si and Si/Sn/Si. The critical step distance is found to change with the substrate temperature, T, in an approximate form, square-root A exp( - E/2kT), which increases much with the Sn layer.