LOW-ENERGY-ELECTRON DIFFRACTION ANALYSIS OF THE PD(100)-P(2X2)-P4G-ALSURFACE - A BURIED-HETEROATOM STRUCTURE

Dynamical low-energy electron diffraction analysis reveals that the p( 2 x 2)-p4g ordered bimetallic phase formed on aluminum-deposited Pd(10 0) consists of a clock-reconstructed Pd top layer and a strongly buckl ed c(2 x 2)-PdAl second layer. A buried-heteroatom model is proposed t o interpret the obtained structure. The Pd-Al heteroatomic bonding int eraction forces the top-layer Pd atoms to move systematically to make Pd-Al-Pd units. The four-fold hollows of the top layer open up only as a result of the systematic unit formation, in contrast to the squeeze d-adatom type p(2 x 2)-p4g C/Ni(100) surface. (C) 1997 Elsevier Scienc e B.V.