The adsorption of oxygen and water on Ca and CaO films studied with MIES, UPS and XPS

• Published in: Surface science Vol. 602; no. 9; pp. 1622 - 1630
• Main Authors: Bebensee, F., Voigts, F., Maus-Friedrichs, W.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.05.2008; Amsterdam Elsevier Science; New York, NY
• Subjects: Calcium; Calcium oxide; Chemisorption; 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; Metastable induced electron spectroscopy; Physics; Ultraviolet photoelectron spectroscopy; X-ray photoelectron spectroscopy; Chemisorption; Calcium oxide; Calcium; Ultraviolet photoelectron spectroscopy; Metastable induced electron spectroscopy; X-ray photoelectron spectroscopy; Water; Oxygen; Metastable phases; Ultraviolet photoelectron spectra; X-ray photoelectron spectra
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2008.02.011

Metastable induced electron spectroscopy (MIES), Ultraviolet photoelectron spectroscopy (UPS), and X-ray photoelectron spectroscopy (XPS) are employed to study the adsorption of water on Ca and CaO films as well as the adsorption of oxygen on Ca films. Ca films are prepared by evaporation of Ca onto clean Si(1 0 0) substrates. CaO films are produced by Ca evaporation in an oxygen atmosphere at a substrate temperature of 400 °C. Gas adsorption on the Ca films at room temperature, both for oxygen and water, is initiated by complete dissociation of the impinging molecules leading to the formation of Ca–O bonds. Exposure to water furthermore leads to the formation of hydroxyl groups via hydrogen abstraction from water forming a complete surface layer. Hydroxyl groups are also formed upon exposure of CaO films to water, but to a significantly smaller amount compared to Ca films exposed to water.