Ultrasensitive Si nanowire probe for magnetic resonance detection

In this study, we have fabricated a 210 nm-wide and 32 μm-long Si nanowire probe with a Si mirror from a silicon-on-insulator wafer. Additionally, a Nd-Fe-B magnet is mounteded at the end of the nanowire for magnetic force detection in MRFM measurements. The fabricated probe shows a resonance frequency f₀ of 11.256 kHz and a Q factor of 12000 after annealing at 800°C for 2 hours in forming gas. The probe exhibits atto-newton sensitivity, and the measurement of force mapping based on electron spin resonance is demonstrated for three-dimensional imaging of radical density. The detected force is approximately 8.5 aN at room temperature.