First Prize: "Nano rings"

Author: Dr Andreas Fuhrer Nanophysics Group of Prof. Ensslin at ETH Zürich Zürich (Switzerland)

AFM nanoelectronics

The image shows a four-terminal quantum ring structure defined in a two-dimensional electron gas (2DEG) with local anodic oxidation using an atomic force microscope tip. The elevated white lines represent the oxide on the surface of the GaAlAs heterosstructure containing the 2DEG. These oxide lines are on average 15nm high and penetrate just as deep into the sample surface, forming barriers in the electron gas below. The ring has an average diameter of 1 micron and the four outer rectangular areas enclosed by oxide lines are used as in-plane gates to tune the electron density of the four arms of the ring. Measuring Aharonov-Bohm oscillations in the ring conductance this device is used to interferometrically detect the relative phaseshift of Coulomb blockade resonances in two quantum dots induced in the arms of the ring.