Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 11: Neue Materialien

HL 11.5: Vortrag

Montag, 8. März 2004, 16:15–16:30, H14

Compton scattering on alkali-metal doped silicon clathrates and gas hydrates — •Martin Volmer¹, Christian Sternemann¹, John S. Tse², Dennis D. Klug², Craig L. Bull³, Paul F. McMillan⁴, Michael Paulus¹, Christian Gutt¹, Thomas Buslaps⁵, and Nozomu Hiraoka⁵ — ¹EIa , University of Dortmund, Dortmund,Germany — ²Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Canada — ³Davy Faraday Research Laboratories, Royal Institution of Great Britain, London, England — ⁴Department of Chemistry, University College London, London, England — ⁵ESRF, Grenoble, France

Si clathrates are guest-host materials in which a dopand is trapped in cage-like structures build up from covalently bonded, four-coordinate Si atoms. Of special importance is the guest-host interaction in silicon clathrate in order to reach a deeper understanding of the electronic properties of these candidates for thermoelectric applications. Thus Compton profiles of the empty caged Si₁₃₆ structure II clathrate and of the alkali-metal-doped M_xSi₄₆ (M_x = Na₈, K₈, Rb₆) structure I calthrates as well as polycrystalline Si have been measured at the Compton scattering beamline ID15B at the ESRF. They are compared with GGA-LDA calculations of these systems and discussed in terms of charge transfer between the guest and the host lattice. Furthermore we measured the Compton profiles of gas hydrates having the different guests namely methane, argon and krypton. In contrast to the Si clathrates, the guest host interaction in the gas hydrates is found to be almost negligible within the limits of our experiment.