Shear force scanning near-field optical microscope based on a piezoelectric bimorph cantilever

In this article we present a simple, nonoptical shear force detection scheme to control probe–sample distance for a scanning near-field optical microscope (SNOM). Shear force detection is realized by attaching a tapered optical fiber probe to a piezoelectric bimorph cantilever in which one piezo layer generates a maximum piezo voltage when the cantilever is excited at resonance by the other piezo layer. The amplitude of the piezo voltage will decrease as the probe approaches a sample's surface due to probe–sample interacting shear force. Keeping the piezo voltage constant provides a very sensitive method by which to control probe–sample distance. Based on the shear force detection scheme, a shear force SNOM system has been built, operating in transmission collection mode. Shear force topographic and optical images have been taken using uncoated optical fiber probes fabricated by a chemical etching technique. The results suggest that the system is very reliable, repeatable, and easy to use.