Magnetic field and temperature dependence of an AFM-defined quantum point contact

We report on the transport properties of a quantum point contact defined by local anodic oxidation using an atomic force microscope on an AlGaAs/GaAs two-dimensional electron gas. Quantization of the conductance G in units of 2e(2)/h has been observed for temperatures ranging from 1.4 to 30 K. The evolution of the conductance plateaus has been studied as a function of the perpendicular magnetic field. The observed behavior agrees well with the one predicted and experimentally found on surface gated quantum point contacts.