Aharonov-Bohm oscillations of a tuneable quantum ring

Using an atomic force microscope a ring geometry with self-aligned in-plane gates was directly written into a GaAs/AlGaAs heterostructure. Transport measurements in the open regime show only one transmitting mode and Aharonov-Bohm oscillations with more than 50% modulation are observed in the conductance. The tuning via in-plane gates allows one to study the Aharonov-Bohm effect in the whole range from the open ring to the Coulomb-blockade regime.