Atomic force microscopy using a piezoresistive cantilever

An atomic force microscope (AFM) is an instrument which measures the topography of a surface by bringing a cantilever beam into contact with a sample and measuring the deflection of the cantilever as it is scanned across the surface. The complexity of an AFM is predominantly governed by the detector used for measuring the deflection of the cantilever probe. The authors describe the fabrication of a silicon cantilever beam with an integrated piezoresistor for sensing its deflection. A silicon-on-insulator material is used for the fabrication. A p-type resistor is fabricated at the surface of the cantilever along a <110> direction so that the piezoresistive effect of silicon causes its resistance to vary linearly with its deflection. The cantilevers considered typically have spring constants from 1 to 10 N/m and minimum detectable deflections from 1 to 10 AA over a 10-Hz-1-kHz frequency range. The cantilevers were successfully used in an AFM, and an image of a grating was obtained with this technique.<>