The structure of Sb-terminated GaAs(001) surfaces

We have studied the structure of Sb-terminated GaAs(001) surfaces using reflection high energy electron diffraction, X-ray photoelectron spectroscopy, and scanning tunneling microscopy (STM). Clean, As-terminated (2×4) surfaces were prepared by molecular beam epitaxy and then exposed to Sb4 at 490°C, producing a (2×8)-reconstructed surface terminated with ~1 ML of Sb. Re-heating such a surface to 460°C in vacuum returns the surface to a (2×4) reconstruction with approximately 0.5 ML Sb remaining. STM reveals a complex, but well-ordered structure on the (2×8) surface for which a tentative model is proposed. On the (2×4) surface, our results clearly show that each unit cell is terminated by three dimers, with two-thirds Sb dimers and one-third As dimers. These results contrast with previous proposals that the Sb-induced (2×4) surface is terminated solely by one or two Sb dimers. © 1999 Elsevier Science B.V. All rights reserved.