Different Growth Modes of Al on Si(111)7 ×7 and Si(111)√3×√3–Al Surfaces

Abstract

Initial growth modes of Al atoms on Si(111)7 ×7 and on Si(111)√3×√3–Al surfaces were clarified by energy-filtered reflection high-energy electron diffraction (EF-RHEED). The growth experiments were carried out at room temperature with a deposition thickness up to about 15 Å. The EF-RHEED patterns and the intensity oscillation curves of the reflection beams were observed under the condition of the energy loss threshold Eloss=30 eV of the retarding potential in order to decrease the background intensity. It was found that, in the case of the Al/Si(111)7 ×7 system, Al atoms grow as three-dimensional islands with the orientations Al(001) ∥Si(111) and Al[110] ∥Si[110] accompanying a twelvefold symmetry axis due to the combination of the fourfold symmetry [Al(001) deposition plane] and threefold symmetry [Si(111) substrate surface]. However, in the case of the Al/Si(111)√3×√3–Al system, Al atoms exhibit an almost two-dimensional layer-by-layer growth mode with Al(111) ∥Si(111) and Al[110] ∥Si[110]. In the latter case, a newly proposed entirely filled T4 site (EFT) surface structure in the transient growth stage is expected to play an important part in achieving excellent epitaxial growth of Al(111).