Interface and Bulk Effects in the Attenuation of Low Energy Electrons Through CaF<sub>2</sub> Thin Films

Physical Review B 58, 2233 - 2239 (1998)

Interface and Bulk Effects in the Attenuation of Low Energy Electrons Through CaF2 Thin Films

J.E. Ortega, F.J. García de Abajo, P.M. Echenique, J. Manke, T. Kalka, M. Dähne-Prietsch, D. Ochs, S.L. Molodtsov, A. Rubio

We have studied for low kinetic electron energies the attenuation of the Si 2p core-level photoemission line through epitaxial CaF2 layers deposited on Si(111). Using an exponential attenuation model we have separated bulk and interface effects, which are, respectively, comprised within energy-dependent bulk attenuation length and interface transmission probability. The attenuation length has basically a constant value of ~ 23 Å for kinetic energies above ~EF+15 eV, whereas the transmission probability has a maximum at ~ 23 eV above EF. The latter effect is consistent with the presence of a large density of bulk Λ1 states in the conduction band of CaF2 around 23.5 eV. Such a large density of states is obtained in a band calculation using the local-density approximation, and it is also detected in the background of secondaries of the photoemission spectra.

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http://dx.doi.org/10.1103/PhysRevB.58.2233

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