Abstract
We have studied the surface atomic structure and electronic properties of the molecular-beam-epitaxy-grown AlAs(001)-(3×2) film by in situ scanning tunneling microscopy and spectroscopy. A structural model is proposed for AlAs(001)-(3×2), in which the ×2 ordering arises from the formation of unusual double π-bonded As dimers along the [110] direction and the ×3 ordering results from the missing As-dimer rows in the [110] direction on the topmost As-terminated layer. Scanning tunneling spectroscopic study directly reveals the energies and spatial locations of the surface states.