ATOMIC-STRUCTURE OF AL-GAAS(110) INTERFACES

Atomic structures of Al on GaAs(110) are studied by ab initio molecular dynamics for coverages of 1/8 to 1 monolayer (ML). A single chemisorbed Al atom resides at the center of a triangle of one Ga and two As atoms. Al dimers have very long bond lengths and bind due to substrate-mediated interactions. Epitaxial growth of 1 ML of Al is less stable than the formation of islands. Preformed clusters bond strongly to the substrate, which shows that the absence of Fermi-level pinning in samples grown by cluster deposition is due to suppression of reactivity rather than lack of interactions.