Adsorption of H2O on Potassium Films

Hans Bonzel, Gerd Pirug, Adolf Winkler

Publikation: Beitrag in einer FachzeitschriftArtikelBegutachtung

Abstract

The interaction of H2O with K films of 30-110 Å thickness was studied at 125 K under ultra-high vacuum conditions utilizing photoemission spectroscopies (XPS, UPS) and measurements of work function as analytical techniques. The K films were grown in situ on a Pt(111) substrate. The interaction of H2O with the K films was found to be complex and included the following processes: adsorption, dissociation and formation of KOH, dissolution and hydration. This reaction proceeded throughout the bulk of the initial K film at 125 K until it was completely transformed into a mixed KOH H2O layer. At this stage a thick ice layer could be grown on top of the mixed KOH H2O film. The conversion of K into KOH H2O was also characterized by a decreasing intensity of plasmon excitation peaks, as observed in connection with K 2p spectra, and by an up-shift of K 2p and K 3p core level binding energies. H2O molecules in the ice layer, dissolved H2O and OH species could be distinguished by their O1s core level and valence orbital binding energies. The dissolved H2O was stoichiometrically linked to KOH and identified as hydration water. Its desorption temperature was considerably higher (280 K) than that of adsorbed H2O ( ~ 160 K). The KOH layer was thermally stable up to 580 K. The clean K film and the KOH layer had work functions of 2.2 and 1.5 eV, respectively. The KOH layer showed an at least ten-fold increase in secondary electron emission below 6 eV kinetic energy (UPS).
Originalspracheenglisch
Seiten (von - bis)287 - 312
FachzeitschriftSurface Science
Jahrgang175
Ausgabenummer2
DOIs
PublikationsstatusVeröffentlicht - 1986
Extern publiziertJa

Treatment code (Nähere Zuordnung)

  • Experimental
  • Basic - Fundamental (Grundlagenforschung)

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