The atomic arrangement of the As-rich (001)-(2 x 4) surface was determined by using bias-dependent scanning tunnelling microscopy and first-principles electronic structure calculations. The scanning tunnelling microscopic images revealed the relative positions and depths of the atomic-scale features within the trenches between the top-layer As dimers. These were in agreement with the β2(2 x 4) structural model. The bias-dependent simulated scanning tunnelling microscopic images revealed that a retraction of the top-most dangling bond orbitals was the novel electronic mechanism that permitted the scanning tunnelling microscope tip to image the trench structure.

Atomic Structure of the GaAs (001)-(2 x 4) Surface Resolved Using Scanning Tunnelling Microscopy and First-Principles Theory V.P.LaBella, H.Yang, D.W.Bullock, P.M.Thibado, P.Kratzer, M.Scheffler: Physical Review Letters, 1999, 83[15], 2989-92