Growth of Twinned Epitaxial Layers on Si(111)√3×√3-B Studied by Low-Energy Electron Microscopy

Abstract

Low-energy electron microscopy (LEEM) was used to investigate Si homoepitaxial growth on Si(111)√3×√3-B. Dark-field LEEM images using the (1,0) spot clearly indicate that two-dimensional islands twinned with respect to the substrate nucleate in the initial growth stage. Coalescence of the twinned islands forms twinned epitaxial layers at low growth temperatures. At high temperatures, however, twinned islands are transformed into untwinned islands even during growth, which suggests that small islands favor the twinned orientation, but that the energy difference between twinned and untwinned islands is reversed at a certain island size. After twinned epitaxial layer growth, we also observed transformation into untwinned layers by annealing. The transformation proceeds through the motion of the boundary between twinned and untwinned layers along the surface.

Molecular beam epitaxial growth of Si on heavily boron-doped Si(111) surface: From initial stages to the growth of Si polytypes

“…In this case, however, a fourfold periodicity was found only partly across the layer stack indicating that during annealing at 1000 K 4-bilayers thick Si layers in twin positions are less stable. This agrees to recent STM and LEEM investigations [4,11]. …”

Trends in low energy electron microscopy

“…This contrast arises because the bulk stacking in wurtzite materials produces a 60 • rotation of the hexagonal unit cell across a bilayer high step. Twinned epitaxial Si islands grown on the Si(111)-B ( √ 3 × √ 3)R30 • surface that are rotated by 180 • with respect to the substrate were also detected using integer-order dark-field imaging conditions [36]. Similar integer-order dark-field imaging of the Ru(0001) surface exhibited contrast between terraces separated by a single atomic step [37].…”