Development of liquid-environment frequency modulation atomic force microscope with low noise deflection sensor for cantilevers of various dimensions

We have developed a liquid-environment frequency modulation atomic force microscope FM-AFM with a low noise deflection sensor for a wide range of cantilevers with different dimensions. A simple yet accurate equation describing the theoretical limit of the optical beam deflection method in air and liquid is presented. Based on the equation, we have designed a low noise deflection sensor. Replaceable microscope objective lenses are utilized for providing a high magnification optical view resolution: 3 m as well as for focusing a laser beam laser spot size: 10 m . Even for a broad range of cantilevers with lengths from 35 to 125 m, the sensor provides deflection noise densities of less than 11 fm/ Hz in air and 16 fm/ Hz in water. In particular, a cantilever with a length of 50 m gives the minimum deflection noise density of 5.7 fm/ Hz in air and 7.3 fm/ Hz in water. True atomic resolution of the developed FM-AFM is demonstrated by imaging mica in water. © 2006 American Institute of Physics. DOI: 10.1063/1.2188867