The coverage-dependent growth structures formed by Mg deposition on GaAs(110) have been studied using scanning tunneling microscopy (STM) and synchrotron-radiation photoemission. In the low-coverage regime at 300 K, Mg adatoms bond on a bridge site between one Ga and two As surface atoms to form two-dimensional domains with local 2×1 structure. Dual-bias STM imaging shows a higher density of unoccupied states than occupied states for these Mg atoms, indicating charge transfer from Mg to the substrate. This 2×1 overlayer is replaced by three-dimensional clusters when the local atom density increases and chemical intermixing is initiated. With increased Mg deposition, the heterogeneous surface region becomes more uniformly reacted and the clusters coalesce. By ∼10-monolayer deposition, the resulting polycrystalline film is locally smooth, although atomic height steps are evident and there are a large number of dislocations.

• Received 15 April 1991

DOI:https://doi.org/10.1103/PhysRevB.44.8843