An STM study of the adsorption of Pb on Cu(100): Formation of an ordered surface alloy
Résumé
The adsorption of Pb on Cu(100) from 0 to 1 ML was investigated by UHV scanning tunneling microscopy. We obtained atomic resolution images of the different superstructures which appear at 300 K with increasing coverage (c(4 x 4), c(2 x 2) and c(5 root 2 x root 2)R45 degrees). We confirm recent results and propose, partly on the basis of low temperature studies, new arguments in favour of an incorporation of lead atoms in the surface layer of copper for low coverage. We demonstrate that the c(4 x 4) superstructure corresponds to an ordered surface alloy of Pb3Cu4 composition, by investigating separately the alloying and de-alloying transitions. De-alloying occurs during the first-order transition between the c(4 x 4) and c(2 x 2) superstructures.