Hamburg 2001 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 2: Elektrische und optische Eigenschaften II
DF 2.3: Fachvortrag
Montag, 26. März 2001, 15:30–15:50, S18/19
Measurement of the local dielectric function across a Σ13 grain boundary in SrTiO-0.5ex3 — •Klaus van Benthem1, Roger H. French2, Wilfried Sigle1, Christian Elsässer1 und Manfred Rühle1 — 1MPI für Metallforschung, Seestraße 92, D-70174 Stuttgart — 2DuPont Central Research, E356-384, Exp. St., Wilmington, Delaware 19880-0356
The valence electron energy-loss spectrum (VEELS) can be described as the imaginary part of the negative reciprocal dielectric function. A Kramers-Kronig analysis of the VEELS therefore leads to a determination of the complex dielectric function of the investigated material, from which all optical properties as well as the electronic structure of the investigated material can be calculated.
In this work the local dielectric fuction of a near Σ13 grain boundary in SrTiO-0.5ex3 has been analysed by measuring spatially resolved VEELS in a scanning transmission electron microscope (STEM)[1]. The local electronic structure could be investigated by comparing the extracted interband transition strength to density of states of ab-initio bandstructure calculations which were performed in the local density approximation for bulk SrTiO-0.5ex3.
Since valence electron excitations are known to be delocalized in space we have measured these effects as a function of the valence electron excitation energy. The results are discussed and compared to theoretical predictions given in the literature.
[1] K. van Benthem, R.H. French, W. Sigle, C. Elsässer, and M. Rühle, Ultramicroscopy (2001)