Graphene-based Hall sensors for scanning magnetic microscopy*

Incorporating few-layer graphite gate electrodes and hexagonal boron nitride gate dielectrics into graphene devices provides an accessible route to create two-dimensional electron systems with extremely low charge inhomogeneity. Here, we fabricate micrometer-scale graphene Hall sensors that can be tuned to a carrier density of ~2×10⁹ cm^-2 at cryogenic temperatures. This translates to a Hall coefficient exceeding 300,000 Ω/T, two orders of magnitude larger than previously reported in any other Hall sensor. The magnetic resolution of our devices is ultimately limited by low-frequency flicker (1/f) and random telegraph noise, and we reach a minimum magnetic field noise spectral density of 60 nT/Hz^1/2 at 1 kHz. Together, our results suggest that these devices have the potential to outperform semiconductor-based Hall sensors. We will also discuss our progress towards fabricating submicron-scale graphene-based scanning Hall probes that function over a wide range of temperatures and magnetic fields.