Valence changes of Sm atoms adsorbed on Mo (2 1 1) surface

• Published in: Surface science 2008-12, Vol.602 (24), p.3721-3727
• Main Authors: Kuchowicz, M., Kołaczkiewicz, J.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; LEED; Physics; Rare-earth metals; STM; X-ray photoelectron spectroscopy
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2008.10.007

Adsorption of Sm thin layers on the Mo (2 1 1) face was investigated by using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), X-ray photoemission spectroscopy (XPS) and changes of the work function measurements (Δ ϕ). The layer growth mode and the valence change of Sm atoms were determined. The Sm layer growth mode is layer-by-layer, at least to 3 ML, followed by the crystallite growth. It was found out that for θ < 0.3 ML Sm atoms are adsorbed only in divalent state. At coverage about 0.5 ML the number of both trivalent and divalent atoms is comparable. At θ = 1 ML, 11% of Sm atoms are divalent, and 89% trivalent. The second layer is composed of only divalent atoms. The first two layers have different surface densities, namely 6.15 × 10 14 atoms/cm 2 for the first layer, and 5.56 × 10 14 atoms/cm 2 for the second. Divalent Sm atoms creating the second layer form islands with the p(3 × 1) structure observed by LEED and STM.