Identification of the adsorption sites of molecular oxygen on Si(111) using XPS

• Published in: Progress in surface science 1995-12, Vol.50 (1), p.315-324
• Main Authors: Lamontagne, B., Roy, D., Sporken, R., Caudano, R.
• Format: Article
• Language: English
• Subjects: Adsorbed layers and thin films; Adsorption and desorption kinetics; evaporation and condensation; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; General and physical chemistry; Photoemission and photoelectron spectra; Physics; Solid-fluid interfaces; Solid-gas interface; Surface physical chemistry; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0079-6816; 1878-4240
• DOI: 10.1016/0079-6816(95)00065-8

Most of the oxygen adsorb dissociatively on Si, however there is also a significant amount of metastable molecular oxygen chemisorbed on Si. The adsorption site/configuration of these molecular oxygen species is still a controversial subject. New XPS results for oxygen adsorption on Si(111) 7×7 (150K) are presented. They reveal four distinct oxygen components; one of the metastable components has never been reported before. We tentatively identify them as: i) stable oxide (Si-O-Si bridges)(~532 eV), ii) diffusing oxygen atom (~533 eV) in silicon oxide and iii) metastable molecular oxygen species (~527.6 eV and ~530.6 eV). The latter have been attributed to peroxy radical which is defined as a diatomic oxygen bonded to a single Si adatom. Our results allow us to distinguish the two main configurations of peroxy radical: paul-para and grif. Both of them possess a lifetime of ~ 180 min.