Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 47: Quantendr
ähte und Korrelationseffekte
HL 47.3: Vortrag
Freitag, 12. März 2004, 11:30–11:45, H15
High frequency measurements on an AFM-structured quantum point contact — •C. Fricke1, J. Regul1, F. Hohls1, R. J. Haug1, D. Reuter2, and A. D. Wiek2 — 1Institut für Festkörperphysik, Abteilung Nanostrukturen, Universität Hannover — 2Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
We fabricated a single quantum point contact by Atomic Force Microscope
(AFM) lithography. We used a diamond
tip for structuring the two dimensional electron gas (2DEG) realized by a
GaAs/AlGaAs-heterostructure.
The 2DEG is about 50 nm below the surface. Isolated areas were written by
about 10 nm deep lines.
The quantum point contact was designed for high frequency measurements
using a special scheme with strip-lines
to source and drain contact and with nonmetallic in-plane-gates.
Our measurements show the frequency dependence of the imaginary part of
the complex admittance between 100 and 400 MHz.
Therefore a very accurate measurement of the phase was necessary.
The real part of the admittance shows a good agreement with DC
characterization.
For the imaginary part we observe a linear frequency dependence as
expected by theory.