Atomic structure determination for GaAs(001)-(6x6) by STM

We present a model structure for the GaAs(001)-(6 x 6) reconstructed surfac e based on high-resolution scanning tunneling microscopy images. This surfa ce has previously also been referred to as (1 x 6), (2 x 6), (3 x 6) and (2 x 6)/(3 x 6) mixed, and contributes to the "4 x 6" mixed surface. Phase co existence with the Ga-rich c(8 x 2) is used to determine the basic structur e. Chemically selective halogen (Cl-2) adsorption is used to distinguish Ga atoms from As atoms and to extract structural details that are not visible in scanning tunneling microscopy images of the clean surface. The structur e is consistent with the electron-counting rule. Partial disorder appears i n the structure. While some of the disorder is due to kinetic barriers to e quilibrium, some is intrinsic to the structure. (C) 1999 Elsevier Science B .V. All rights reserved.