Deeper Insight into Depth-Profiling of Aqueous Solutions Using Photoelectron Spectroscopy

Research output: Contribution to journalArticle

Abstract

X-ray photoelectron spectroscopy (XPS) is widely used to probe properties such as molecular stoichiometry, microscopic distributions relative to the surface by so-called depth-profiling, and molecular orientation. Such studies usually rely on the core-level photoionization cross sections being independent of molecular composition. The validity of this assumption has recently been questioned, as a number of gas-phase molecules have been shown to exhibit photon-energy-dependent nonstochiometric intensity oscillations arising from EXAFS-like modulations of the photoionization cross section. We have studied this phenomenon in trichloroethanol in both gas phase and dissolved in water. The gas-phase species exhibits pronounced intensity oscillations, similar to the ones observed for other gas-phase molecules. These oscillations are also observed for the dissolved species, implying that the effect has to be taken into account when performing depth-profiling experiments of solutions and other condensed matter systems. The similarity between the intensity oscillations for gas phase and dissolved species allows us to determine the photoelectron kinetic energy of maximum surface sensitivity, approximate to 100 eV, which lies in the range of pronounced intensity oscillations.

Details

Authors
  • Olle Bjorneholm
  • Josephina Werner
  • Niklas Ottosson
  • Gunnar Öhrwall
  • Victor Ekholm
  • Bernd Winter
  • Isaak Unger
  • Johan Soderstrom
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Natural Sciences
  • Physical Sciences
Original languageEnglish
Pages (from-to)29333-29339
JournalJournal of Physical Chemistry C
Volume118
Issue number50
StatePublished - 2014
Peer-reviewedYes