Regensburg 2010 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 8: Electrical and mechanical properties
DF 8.2: Talk
Tuesday, March 23, 2010, 14:20–14:40, H9
Space-charge wave excitation by static and moving interference patterns in Bi12GeO20 — •Burkhard Hilling, Thomas Schemme, Kay-Michael Voit, Heinz-Jürgen Schmidt, and Mirco Imlau — Department of Physics, University of Osnabrück, Germany
We report on space-charge wave (SCW) excitation in semi-insulating materials by simultaneous exposure with a static and a moving interference pattern and the application of a static electric field [1]. The two patterns with equal spatial frequency are generated independently from each other using a four-beam interferometer with only one light source. A single crystal of BGO (Bi12GeO20) was applied as an example; the investigations were performed at a wavelength of 514 nm using a total light intensity of 30 mW/cm2, spatial frequencies of (0.5−12)· 103 cm−1, and electric fields ≤ 10 kV/cm. This method enables us to determine the sign of the charge carriers participating in SCW formation. Compared to the classical method using an oscillating interference pattern, this method increases the quality factor of the excited SCW [1]. The latter enabled studies with samples of thicknesses d=0.12−2.0 mm cut from the same boule. Also the dependence of the SCW-signal on the direction of the electric field with respect to the crystallographic axes is studied. Remarkably, SCW excitation is independent from the sample’s thickness and the orientation of the crystallographic axes. Hence, we can suggest, that it can be applied also to very thin samples (d≪1 µm), e.g., to semiconductor films. Financial support from the DFG (GRK 695) is gratefully acknowledged.
[1] B. Hilling et al., PRB 80, 205118 (2009)