Characterization and optimization of the detection sensitivity of an atomic force microscope for small cantilevers

The detection sensitivity of an atomic force microscope with optical beam d eflection for small cantilevers is characterized experimentally and theoret ically. An adjustable aperture is used to optimize the detection sensitivit y for cantilevers of different length. With the aperture, the signal-to-noi se ratio of cantilever deflection measurements is increased by a factor of 1.5 to nearly 3. A theoretical model is set up that generally describes the optical beam deflection detection in an atomic force microscope. This mode l is based on diffraction theory and includes the particular functional sha pe of the cantilever. (C) 1998 American Institute of Physics. [S0021-8979(9 8)01021-4].