Surface-plasmon energy shifts due to submonolayer molecular adsorption on silver and aluminum

• Published in: Physical review. B, Condensed matter Condensed matter, 1989-01, Vol.39 (2), p.1006-1012
• Main Authors: MILLO, O, GOLDSTEIN, Y, MANY, A, GERSTEN, J. I
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Metals, semimetals and alloys; Metals. Metallurgy; Physics; Specific materials; Surface and interface electron states
• ISSN: 0163-1829; 1095-3795
• DOI: 10.1103/PhysRevB.39.1006

The effect of submonolayer molecular adsorptions on the surface-plasmon spectrum of Ag and Al surfaces is investigated using low-energy electron-loss spectroscopy. Plasmon energy shifts of approx 200 and 500 meV for one-monolayer hydrocarbon coverage were observed on Ag and Al films, respectively. In addition, a new loss peak appears upon adsorption, which is associated with a molecular electronic resonance. Its energy shifts with increasing coverage in the opposite direction to that of the plasmon. A classical dielectric model is presented in which the losses are attributed to two branches of a collective excitation in a system consisting of (adsorbate) oscillators on top of a semi-infinite metal surface. Graphs, Spectra. 30 ref.--AA(US).