THE ROLE OF INTERFACIAL STRAIN IN THE SURFACE P4G RECONSTRUCTION - A COMPARISON BETWEEN PD(001)-(2X2)P4G-AL AND CU3PT(001)

The surface composition and structure of the Pd(001)(2 x 2)p4g-Al phas e have been studied by low-energy ion scattering (LEIS) and low-energy electron diffraction (LEED). It was found that annealing Al-covered s urfaces with initial coverages from half to larger than one monolayer (ML) to about 900 K gave rise to a stable (2 x 2)p4g LEED pattern. The ion scattering data suggest that the reconstruction is due to an orde red c(2 x 2) Al-Pd underlayer below a clock-rotated (001) Pd terminati on. To better understand the Pd(001)-(2 x 2)p4g-Al system, we have als o studied an ordered Cu3Pt(001) alloy surface, which exhibits the stab le c(2 x 2) structure with an ordered c(2 x 2) Cu-Pt underlayer below a (1 x 1) Cu termination. Strain analysis shows that the top-layer rec onstruction for the (2 x 2)p4g surface is caused by the Al-induced int erfacial strain.