Low Energy Electron Interaction with Molecules at Surfaces

  • Eugen Illenberger


Electron initiated processes play a key role in any kind of laboratory plasma. It is primarily the electron-molecule interaction from which the feed gas molecules receive energy and which maintains the plasma. These primary interactions generate molecules in various excited states, in ionized forms (cations and anions) and finally as fragmentation products, also in excited and ionized forms1. All these particles mutually interact, incuding photons from emission processes. It is hence a vast variety of different interactions between primary and secondary particles which characterize a plasma. In principle, knowledge about the relative density of the components in their different states and the respective cross sections would be necessary to model and eventually control the plasma. In actual pactice, however, it is often sufficient to restrict on two body interactions between the most abundant components which, in the case of laboratory plasmas, are usually electrons and neutral gas molecules. The plasmas used in materials processing are often so called cold or anisothermic plasmas.2 Although they contain a variety of high energy species (neutrals, radicals and ions in excited states) the plasma does not considerably heat its container, i. e., the excited species are far from equilibrium. In particular, the electron energy distribution in such a cold plasma peaks at a few eV and is hence much higher than the average energy of the heavy particles (kT (300K) = 0.026 eV). The weak coupling between the electrons and heavy particles is a consequence of the large difference in masses. From energy and momentum conservation it follows that in a collision, an electron can only transfer an energy amount of the order m/M (m: electron mass, M: mass of the heavy particle) onto the heavy target. Exceptions are low energy electron collisions with polar molecules, collisions when resonances are involved (see below) but also collisions at higher energies when electronic excitation becomes accessible.


Electron Attachment Dissociative Electron Attachment Electron Stimulate Desorption Geometrical Cross Section Total Ionization Cross Section 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    K. H. Becker, Elementary collision processes in plasmas, in Low Temperature Plasma Physics, R. Hippler, S. Pfau, M. Schmidt and K. H. Schoenbach (Eds.) Wiley-VCH Berlin, 2001.Google Scholar
  2. 2.
    A. Grill, Cold Plasma in Material Fabrication. From Fundamental to Applications, IEE Press, New York 1994.Google Scholar
  3. 3.
    Y. Hatano, Physicochemical Aspects of Atomic and Molecular Processes in Reactive Plasmas, Adv. At. Mol. Opt. Phys. 43, 231–241 (2000).CrossRefGoogle Scholar
  4. 4.
    H. Deutsch, K. Becker, S. Matt and T. D. Mark, Theoretical determination of absolute electron-impact ionization cross sections of molecules, Int. J. Mass Spectrom. 197, 37–69 (2000).CrossRefGoogle Scholar
  5. 5.
    E.C. Zipf, Dissociation of Molecules by Electron Impact, in Ref. 6.Google Scholar
  6. 6.
    L.G. Christophorou (Ed.), Electron-Molecule Interactions and Their Applications, Vols I and II, Academic Press, Orlando, FL, 1984.Google Scholar
  7. 7.
    E. Illenberger, J. Momigny, Gas Phase Molecular Ions. An Introduction to Elementary Processes Induced by Ionization, Steinkopff, Darmstadt, Springer, New York 1992.Google Scholar
  8. 8.
    D. Klar, M.-W. Ruf and H. Hotop, Dissociative electron attachment to CC14 molecules at low electron energies with meV resolution, Int. J. Mass Spectrom. 205, 93–110 (2001).CrossRefGoogle Scholar
  9. 9.
    H. Ibach and D. L. Mills, Electron Energy Loss Sepctroscopy and Surface Vibrations, Academic Press, New York, 1982.Google Scholar
  10. 10.
    L. Sanche, Low energy electron scattering from moelecules at surfaces, J. Phys. B: At. Mol. Opt. Phys. 23 1597–1624 (1990).CrossRefGoogle Scholar
  11. 11.
    E. Illenberger, Electron Capture Processes by Free and Bound Molecules, in Photoionization and Photodetachment, Part II, Advanced Series in Physical Chemistry Vol. 10B, C.-Y. Ng (Ed.), World Scientific, Singapore, 2000.Google Scholar
  12. 12.
    O. Ingolfsson, F. Weik and E. Illenberger, The Reactivity of Slow Electrons with Molecules at Different Stages of Aggregation: Gas Phase, Clusters and Condensed Phase, Int. J. Mass Spectrom. 155, 1–68 (1996).CrossRefGoogle Scholar
  13. 13.
    M. Meinke, L. Parenteau, P. Rowntree, L. Sanche and E. Illenberger, Low Energy Electron Stimulated Desorption of Anions from Condensed CF4, Chem. Phys. Letters, 205,213–218(1993).CrossRefGoogle Scholar
  14. 14.
    A. D. Bass, J. Gamache, L. Parenteau and L. Sanche, Absolute Cross Section for Dissociative Electron Attachment to CF4 Condensed onto Multilayer Krypton, J. Phys. Chem. 99, 6123–6127 (1995.)CrossRefGoogle Scholar
  15. 15.
    I. Le Coat, N. M. Hedhili, R. Azria, M. Tronc, O. Ingólfsson and E. Illenberger, Medium Enhanced, Electron Stimulated Desorption of CF3- from Condensed CF3I, Chem. Phys. Letters 296, 208–214 (1998).CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Eugen Illenberger
    • 1
  1. 1.Institut fuer Chemie-Physikalische und Theoretische ChemieFreie Universitaet BerlinTakustrasse 3BerlinGermany

Personalised recommendations