Scanning tunneling microscopy and first-principles theory of the Sn/GaAs(110) surface

Scanning tunneling microscopy of Sn overlayers on the GaAs(110) surface shows patterns with local order of nominal (3×3) periodicity and an absence of long-range order. Using first-principles calculations, we show that these observations can be explained in terms of a double-layer structure which consists of a complete (1×1) Sn layer covered by Sn adatoms. This structure results from a subtle balance between electronic energy and lattice strain. Spectroscopic studies indicate that this Sn overlayer exhibits a narrow gap (<0.2 eV) centered in the gap region of the GaAs substrate. © 1989 The American Physical Society.