Sn-mediated transformations on Si(111) surface: Reconstructions, Electromigration, Homoepitaxy

We have studied Si mass transport and morphological transformations on the Si(111) surface during (root 3 x root 3)-Sn reconstruction formation and following Si homoepitaxy in 600-825 degrees C interval by in situ ultrahigh vacuum reflection electron microscopy (UHV REM) and ex situ atomic force microscopy (AFM). We have shown that the formation of a metallic alpha-(root 3 x root 3)-Sn phase during Sn deposition at T < 650 degrees C leads to Si 2D island nucleation on > 1 mu m terraces, while the formation of a mosaic gamma-(root 3 x root 3)-Sn phase at T > 650 degrees C is followed by monatomic step shift in the step-up direction and provides Sn/Si(111) interface with wide atomically flat terraces. The step shift value has been measured as functions of substrate temperature and Sn deposition rate to determine emitted by the steps Si coverage participating in gamma-phase formation. The electromigration-induced drift of disordered 1 x 1-Sn domains has been shown to entail enhanced noncompensated Si mass transport followed by the Si(111)-(root 3 x root 3)-Sn surface roughening. The kinetics of 2D island nucleation and growth near monatomic steps and on wide (up to 10 mu m) terraces on the Si(111)-gamma-(root 3 x root 3)-Sn surface during Si deposition at 700 degrees C is limited by surface diffusion only, and critical nucleus i consists of similar to 20-100 Si atoms.

Automated summary

This study investigates Si mass transport and morphological transformations on the Si(111) surface during (root 3 x root 3)-Sn reconstruction formation and Si homoepitaxy. The research shows that the formation of different Sn phases at different temperatures affects the Si island nucleation and monatomic step shift, which in turn impact the morphology of the Sn/Si(111) interface. Electromigration-induced drift of disordered Sn domains leads to enhanced noncompensated Si mass transport and surface roughening.