Si-induced Island Formation and Surface Ordering on GaAs(001)-c(4×4)

Scanning tunneling microscopy (STM) has been used to study the deposition of Si at 400 °C onto the c(4×4) surface reconstruction of GaAs(001) surfaces grown in situ by molecular beam epitaxy (MBE). Emphasis is placed on the nucleation, island formation, and surface ordering, as a consequence of adsorption onto the c(4×4) surface. With increasing Si coverage, a series of anisotropic ‘‘needlelike’’ islands is formed. A site exchange model is proposed in which the deposited Si atoms displace the top layer As atoms of the c(4×4) structure, with the displaced As atoms forming dimers in a new top layer.