Epitaxial Graphene Sensors for Detection of Small Magnetic Moments

Micron-sized Hall sensors made of epitaxial graphene grown on 4H-SiC(0001) have been fabricated and studied at room temperature using transport and noise spectrum measurements. We report detection of 1-μm Dynal bead with the magnetic moment of ~4×10⁸ μ_B, using a 2-μm epitaxial graphene device. A phase-sensitive AC-DC Hall magnetometry method was used to reliably detect the bead with a relatively large response of V_x^AC ~ 7 μV. Bead positioning was performed using a nanomanipulator inside of the FIB system. Long-term effect of the small dose of e-beam irradiation (~4 × 10¹⁴ e/cm²) on the performance of graphene Hall devices is reported.