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HL: Halbleiterphysik

HL 12: Poster I

HL 12.56: Poster

Montag, 8. März 2004, 16:30–19:00, Poster A

Conductance spectroscopy of an AFM-engraved quantum point contact — •B. Harke¹, C. Fricke¹, F. Hohls¹, R. J. Haug¹, D. Reuter², and A. D. Wieck² — ¹Institut für Festkörperphysik, Abteilung Nanostrukturen, Universität Hannover, Appelstr. 2, 30167 Hannover, Germany — ²Lehrstuhl für angewandte Physik, Ruhr-Universität Bochum, 44780 Bochum, Germany

We used the mechanical Atomic Force Microscope (AFM) lithography to write insulating trenches in a two dimensional electron gas (2DEG) realized by a GaAs/AlGaAs-heterostructure. To get insulated areas in the 2DEG which is located about 50 nm below the surface we wrote 10 nm deep lines to deplete the 2DEG underneath the trench. We achieved isolating lines with a breakdown voltage of at least 20V. For this lithography we used a diamond tip for precise structuring of a quantum point contact with the width of 500nm. Our characterization measurements show distinct quantization of the conductivity in dependence of gatevoltage as expected. Furthermore we show conductance spectroscopy measurements for different magnetic fields. We observe a pronounced 0.7 anomaly which was analyzed in dependence of magnetic field up to 15 Tesla and temperature between 1.5 K and 10 K.