GA-S-GA BRIDGE-BOND FORMATION ON IN-SITU S-TREATED GAAS(001) SURFACE OBSERVED BY SYNCHROTRON-RADIATION PHOTOEMISSION SPECTROSCOPY, X-RAY-ABSORPTION NEAR-EDGE STRUCTURE, AND X-RAY STANDING WAVES

The chemical and structural changes of an in-situ S-treated GaAs(001)s urface induced by thermal treatments were studied by synchrotron radia tion photoemission spectroscopy (SRPES), X-ray absorption near edge st ructure (XANES), and X-ray standing waves (XSW). SRPES results reveale d that As-S chemical states in the As 3d core level disappear from the surface with annealing at 400 degrees C. S K-edge XANES spectra showe d that most of the S atoms are in a S-Ga chemical state after annealin g at about 350-400 degrees C. XSW results suggested that the exchange reaction between the S and As atoms begins to occur at an annealing te mperature lower than 300 degrees C, and that the Ga-S-Ga bridge-bond f ormation is almost completed with annealing at about 350-400 degrees C . (C) 1998 Elsevier Science B.V. All rights reserved.