Sb overlayers on (110) surfaces of III–V semiconductors: A new type of chemical bond

An elastic low‐energy electron diffraction (ELEED) structure analysis of ordered p(1×1) monolayers of Sb on GaAs(110) reveals a puzzle: the Sb atoms form chains within which the bonding is purely p2 but which exhibit tetrahedral (sp3) coordination with the substrate. No bulk or molecular compounds with such properties are known. Using a tight‐binding total‐energy minimization model we predict the atomic geometries of saturated Sb monolayers on the (110) surfaces of GaP, GaAs, GaSb, InP, InAs, and InSb. The known structure for Sb on GaAs(110) is obtained and the prediction for InP(110) is verified by a preliminary ELEED intensity analysis. The same model is used to predict the surface state eigenvalue spectra and to analyze the nature of the Sb‐substrate bonds. The bonds are hybrids between pi states in the Sb chain and sp3 substrate dangling bond orbitals. Their existence is a unique surface phenomenon caused by the structural constraint of epitaxial growth of the Sb monolayer.