Atomic structure of the GaAs((113) over bar)B surface

The GaAs((113) over bar)B surfaces were prepared by molecular-beam epitaxy and were in situ studied by low-energy electron diffraction and scanning tunnelling microscopy. We present results for two different surface structures, the recently observed (8x1) reconstruction and an As-rich structure. For the (8x1) reconstruction we confirm a model that consists of Ga dimer zigzag chains along [(33) over bar2] in two atomic levels. We report on the reflection high-energy electron diffraction (RHEED) during growth. RHEED oscillations are observed mainly with the electron beam along [(1) over bar 10] from which it is concluded that growth occurs through two-dimensional nucleation and propagates along [(33) over bar2]. The As-rich structure represents a remarkable case intermediate between a stable singular and an unstable facetted surface: Locally, As adatoms and dimers create a 1x and a 2x periodicity but long-range order does not exist; nevertheless, the surface comprises large terraces that are separated by well-developed steps