A high-stiffness axial resonant probe for atomic force microscopy

A high-stiffness, (> 500 N/m) resonant atomic force microscope probe was co nstructed to allow force measurements in the presence of large force gradie nts. The probe employs a piezoresistively detected, electrostatically drive n resonant beam sensor oriented perpendicularly to the sample surface. This probe is distinguished from shear force microscopy and noncontact atomic f orce microscopy in that the design allows for a stationary probe tip for im proved spatial resolution and measures forces rather than force gradients. Measured results show a force resolution of 9 nN in a 1-kHz bandwidth in ai r with an oscillation amplitude of 36 mn and a resonance quality of 20. In a 1-mtorr vacuum the force resolution in the same bandwidth improves to 200 pN with a resonance quality of 450 and oscillation amplitude of 53 nm. Thi s resolution is limited by white noise of the piezoresistor, and scales as expected with amplitude and resonance quality.