INTERDIGITAL CANTILEVERS FOR ATOMIC-FORCE MICROSCOPY

We present a sensor for the atomic force microscope (AFM) where a sili con cantilever is micromachined into the shape of interdigitated finge rs that form a diffraction grating, When detecting a force, alternatin g fingers are displaced while remaining fingers are held fixed. This c reates a phase sensitive diffraction grating, allowing the cantilever displacement to be determined by measuring the intensity of diffracted modes. This cantilever can be used with a standard AFM without modifi cation while achieving the sensitivity of the interferometer and maint aining the simplicity of the optical lever. Since optical interference occurs between alternating fingers that are fabricated on the cantile ver, laser intensity rather than position can be measured by crudely p ositioning a photodiode. We estimate that the rms noise of this sensor in a 10 hz-1 kHz bandwidth is similar to 0.02 Angstrom and present im ages of graphite with atomic resolution. (C) 1996 American Institute o f Physics.