MEMS Ring Resonators for Laserless AFM With Sub-nanoNewton Force Resolution

A concept of atomic force microscopy (AFM) oscillating sensors using electromechanical silicon microresonators is presented, and imaging capabilities are demonstrated. The microresonators are designed to feature MHz resonance frequencies, and they are batch fabricated using standard silicon microtechnologies. Integrated capacitive transducers allow to drive the resonator and to sense its vibration amplitude. A nanotip is located at a maximum of displacement for sensing near-field forces when interacting with a surface. The device has been mounted on a commercial AFM setup through a dedicated probe holder and a preprocessing electronic circuit. Experiments show that intermittent contact AFM is possible with a tip vibration amplitude of a few nanometers. AFM images have been acquired on silicon micro and nanopatterns. A force resolution of 0.2 nN/root Hz is deduced from the measurements.