Ca chemisorption on Cu(100) in the submonolayer regime: Metastable and stable adsorption phases

Ca adsorption on Cu(100) has been studied by high-resolution electron energy-loss spectroscopy, work-function measurements, and low-energy electron diffraction as a function of coverage, up to one monolayer, at 110 and 300 K. At each coverage a condensed phase is formed at 110 K that irreversibly transforms into a dispersed phase upon heating. The 300-K data suggest that Ca occupies substitutional sites at this temperature. A comparison with the chemisorption of alkali metals is presented.