INFLUENCE OF SUBSTRATE STEPS ON THE PROPERTIES OF EPITAXIAL NOBLE-METAL FILMS

In this work we report on the influence of surface steps on the growth structure, the energetics and the electronic properties of Ag on a st epped Ru(10 11 7BAR) surface as deduced from TDS, AES, LEED, ARUPS and PAX measurements. Increased desorption temperatures as well as PAX da ta suggest a selective ''decoration'' of the surface step sites at low Ag coverages. In particular no Ag island formation is detected neithe r with PAX, nor with LEED, nor with ARUPS for theta(Ag) < 0.2 ML, in c ontrast to the findings on flat Ru(0001). As an interesting consequenc e, a significant change in the Ag valence band spectra is observed. Wh ile already 0.05 ML Ag on a flat Ru(0001) surface exhibit a clear 4d-s pin-orbit- and crystal-field-splitting of 1.35 eV no such splitting is detectable for up to 0.15 ML Ag on the stepped surface. Furthermore, a quasi-one-dimensional Ag band structure is suggested by ARUPS data f or these low Ag coverages showing a dispersion of the Ag d-states only parallel but not perpendicular to the substrate steps.