Characterization of K and Cs adsorption on Fe(110)

The adsorption of K and Cs on Fe(110) has been studied by low-energy electr on diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectr on spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). At room temperature, no ordered structures were observed until the saturation coverage was reached. At 90 K, the formation of ordered structures takes pl ace above Theta=0.20. The structures are hexagonal with varying density, bu t alignment with respect to the substrate changes between Theta=0.23 and 0. 25. At saturation of the first monolayer, the K-K and Cs-Cs nearest-neighbo r distances are compressed with respect to the bulk values. From the photoe mission data, the onset of metallization of the Cs layers can be detected a t a coverage of about 30% of the saturation coverage. For Cs, a second laye r with a relaxed nearest neighbor distance was observed. From the Cs 4d int ensity vs. coverage curve, a layer-by-layer growth mode can be derived. (C) 1999 Elsevier Science B.V. All rights reserved.