Real-time scanning Hall probe microscopy

We describe a low-noise scanning Hall probe microscope having unprecedented magnetic field sensitivity (∼2.9×10−8 T/√Hz at 77 K), high spatial resolution, (∼0.85 μm), and operating in real-time (∼1 frame/s) for studying flux profiles at surfaces. A submicron Hall probe manufactured in a GaAs/AlGaAs two-dimensional electron gas (2DEG) is scanned over the sample to measure the surface magnetic fields using conventional scanning tunneling microscopy positioning techniques. Flux penetration into a high Tc YBa2Cu3O7−δ thin film has been observed in real time at 85 K with single vortex resolution. Flux is seen to enter the film in the form of vortex bundles as well as single flux quanta, Φ0.