Structural analysis of Si(111)-√21 x √21-Ag surface by reflection high-energy positron diffraction

The atomic structure of Si(111)-root 21 x root 21-Ag surface, which is formedby the adsorption of small amount of Ag atoms on the Si(111)-root 3 x root 3-Ag surface, was determined by using reflection high-energy positron diffraction. The rocking curve measured from the Si(111)-root 21 x root 21-Ag surface was analyzed by means of the intensity calculations based on the dynamical diffraction theory. The adatom height of the extra Ag atoms from the underlying Ag layer was determined to be 0.53 angstrom with a coverage of 0.14 ML, which corresponds to three atoms in the root 21 x root 21 unit cell. From the pattern analyses, the most appropriate adsorption sites of the extra Ag atoms were proposed. (c) 2006 Elsevier B.V. All rights reserved.