Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 1 Ion Scattering Spectroscopy Modern Methods in Heterogeneous Catalysis Research Fritz-Haber-Institut der MPG – WS 2006/07 Lecture Series Heterogeneous Catalysis Dr. Christian Linsmeier Max-Planck-Institut für Plasmaphysik, Garching [email protected]
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Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 1
Ion Scattering Spectroscopy
Modern Methods in Heterogeneous Catalysis ResearchFritz-Haber-Institut der MPG – WS 2006/07
Lecture SeriesHeterogeneous Catalysis
Dr. Christian LinsmeierMax-Planck-Institut für Plasmaphysik, [email protected]
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 2
Ion spectroscopies
1. Ion scattering (elastic interaction)Low-energy ion scattering (ISS or LEIS, ~500 eV — some keV)Medium-energy ion scattering (MEIS, 20 — 200 keV)High-energy or Rutherford backscattering spectroscopy (RBS, ~MeV)Elastic recoil detection analysis (ERD, keV — MeV)
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 20
RBS: Information on depth distribution
Stopping powerelectronic energy lossnuclear energy loss
Bragg’s Rule: Compoundsexact: metallic alloysapproximate (up to 20%):hydrocarbons, oxides,nitrides, …
J.F. Ziegler, Helium - Stopping Powers and Ranges in All Elements,Vol. 4, Pergamon Press, 1977Compound AmBn
SA is stopping power of element ASB is stopping power of element B
SAB = m SA + n SB
-2
eV:atoms cm
1 unitdES ndx= −
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 21
Impregnation of MoO3/Al2O3 model catalysts
Preparationanodic oxidation of Al foilimpregnation of oxide with ammonium heptamolybdate solution
AnalysisMo signal from techniques with different depth information:RBS: ~50 MLAES: ~5 MLISS: 1 ML
Mechanismpore filling (RBS) in less than 1 minmolybdate surface adsorption within hours (ISS)
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 22
RBS: Example depth profile
235 nm W on Be, alloy formation during annealing
depth distribution:determination of depth distribution by comparison of measured with simulatedspectraconsideration of kinematics, scattering cross section, and stopping power
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 23
NRA: Nuclear reaction analysis
Advantage:sensitive for light elementssignal at large channel numbers/energies in spectrum: no background!
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 24
ERD: Elastic Recoil Detection Analysis
Specific feature:one of the very few methods to detect hydrogendiscrimination between hydrogen isotopes possible
2 nm Au / 100 nm AlN / 2 nm Ta / Si a-C:H layer, implanted with 8 keV D+
Measurement: 2.6 MeV He, θ=30°
Dr. Ch. Linsmeier Ion Scattering Spectroscopy Heterogeneous Catalysis FHI 2006/07 - 25
Literature
Books, review articles:1. E. Taglauer, Surface chemical composition, in: Handbook of Heterogeneous Catalysis, Eds. G. Ertl, H.
Knözinger, J. Weitkamp, Vol. 2, Wiley VCH, Weinheim (1997).2. H. Niehus, W. Heiland, E. Taglauer, Low-energy ion scattering at surfaces, Surface Science Reports Vol. 17
(1993).3. E. Taglauer, Low-energy Ion Scattering and Rutherford Backscattering, in: Surface Analysis – The Principal
Techniques, Ed. J. Vickerman, Wiley (1992)4. Eds. D. Briggs and M.P. Seah, Practical Surface Analysis, Vol. 2 – Ion and Neutral Spectroscopy, 2nd ed.,
Wiley (1992).
Journal articles:1. Ch. Linsmeier, H. Knözinger, E. Taglauer, Surf. Sci. 275 (1992) 101.2. M. Aono, C. Oshima, S. Zaima, S. Otani, Y. Ishizawa, Jap. J. Appl. Phys. 20 (1981) L829.3. K. Josek, Ch. Linsmeier, H. Knözinger, E. Taglauer, Nucl. Instrum. Meth. Phys. Res. B64 (1992) 596.4. Th. Fauster, Vacuum 38 (1988) 129.5. H. Niehus, G. Comsa, Surf. Sci. 140 (1984) 186. J.-P. Jacobs, L.P. Lindfors, J.G.H. Reintjes, O. Jylhä, H.H. Brongersma, Catal. Lett. 25 (1994) 315.