ALKALI-METAL ADSORPTION ON DISSIMILAR ALKALI-METAL MONOLAYERS PREADSORBED ON CU(001) - LI ON NA AND NA ON LI

An adsorption system of metal-on-metal growth is presented. The adsorption of alkali-metal atoms on monolayers of dissimilar alkali metals preadsorbed on the Cu(001) surface has been studied by Auger-electron spectroscopy, work-function change, and low-energy electron-diffraction intensity analysis. We have examined the following three adsorption systems on Cu(001) at 180 K; Na on a full monolayer of Li, Li on a full monolayer of Na, and Na on a submonolayer of Li, namely, the c(2×2) structure of Li adatoms. It is found that a simple overlayer formation of Na takes place on the full Li monolayer, while Li atoms substitute Na adatoms for Li adsorption on the full Na monolayer. For adsorption of Na on the Li-c(2×2) structure whose coverage is 5/8 of the full Li monolayer, it is found that Na atoms compress the Li adlayer to become denser monolayers. The Na atoms do not intermix with Li adatoms, but they form islands of the c(2×2) structure on Cu(001). © 1994 The American Physical Society.