The use of direct recoil spectrometry (DRS) for the study of water vapor interactions on polycrystalline metallic surfaces - The H 2 O/U and H 2 O/Ti systems

M. H. Mintz, N. Shamir

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Using direct recoil spectrometry (DRS), the shadowing of surface H atoms by neighboring O atoms can differentiate between full and partial dissociation routes of water molecules on the surface as well as point to the geometrical arrangements of hydroxyl surface groups. The H 2 O/U and H 2 O/Ti systems were compared. It has been found that different mechanisms control the water-surface interactions in these systems. For the H 2 O/U system, a simple direct-collision (Langmuir-type) dissociative chemisorption controls the process. Two consecutive stages were identified: (i) below ∼70% monolayer coverage, a complete dissociation of water into oxygen ion and two H atoms, which chemisorb on the remaining unreacted metallic surface and (ii) above about 70% of a full layer coverage, three dimensional oxide islands start to form, causing partial dissociation of water and the formation of surface hydroxyls. For the H 2 O/Ti system, a more complicated mechanism, which involves a precursor state, seems to control the process. In that case, two concurrent routes act simultaneously. In addition to the simple direct-collision mechanism, water precursor clusters (bound by hydrogen bonds), which partly dissociate, result in chemisorbed tilted hydroxyl clusters (even at low-coverage). The relative contributions of the precursor route and the direct-collision route are pressure dependent, with the former being dominant at higher exposure pressures.

Original languageEnglish
Pages (from-to)633-640
Number of pages8
JournalApplied Surface Science
Volume252
Issue number3
DOIs
StatePublished - 31 Oct 2005

Keywords

  • DRS
  • H O/Ti system
  • H O/U system
  • H shadowing

ASJC Scopus subject areas

  • General Chemistry
  • Condensed Matter Physics
  • General Physics and Astronomy
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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