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-mu m Dynal bead with the magnetic moment of similar to 4 x 10(8) mu(B), using a 2-mu m 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) similar to 7 mu V. Bead positioning was performed using a nanomanipulator inside of the FIB system. Long-term effect of the small dose of e-beam irradiation (similar to 4 x 10(14) e/cm(2))on the performance of graphene Hall devices is reported.