Bismuth and antimony on GaAs(110): Dielectric and electronic properties

An investigation of the metal-induced electronic states, the dielectric properties, and the growth morphology of Bi/GaAs(110) and Sb/GaAs(110)-as model systems, for epitaxial and unreactive interfaces-is presented. The electronic transitions involving surface and Bi (Sb) -induced states, investigated by means of high-resolution electron-energy-loss spectroscopy, are discussed and compared with previous results. In the Bi/GaAs(110) interface, a clear absorption structure appears within the bulk gap, revealing its semiconducting character with a surface gap of 0.65 eV at one monolayer. When an ordered monolayer of Sb is formed, only a slight shift of the absorption edge is observed and the interface shows semiconducting properties. At higher coverages, the different growth morphology and dielectric properties of the Bi/GaAs(110) and the Sb/GaAs(110) interfaces are discussed. Above the first epitaxial and semiconducting monolayer, Bi builds up in a regular structure with a metallic dielectric character before approaching a bulklike crystalline and semimetallic behavior, while Sb grows as an amorphous and semiconducting layer before becoming polycrystalline and semimetallic.