Optical lever detection in higher eigenmode dynamic atomic force microscopy

The optical lever detection scheme is widely used in atomic force microscopy for the detection of the cantilever deflection. Laser spot size as well as adjustment of the laser along the cantilever determine the zeros of the transfer function of the signal path from the tip-sample forces to the optical readout. This can cause (almost) pole-zero cancellations which lead to a significantly reduced sensitivity in the detection of higher mode vibrations of the cantilever. Physically, the light lever detection integrates over the slope of the cantilever. However, the sign of the slope of higher flexural modes varies along the cantilever. Thus, integration can lead to a significantly decreased sensitivity to higher eigenmode vibrations. Illuminating only the area between the free end and the next zero crossing of the slope of the modal shape provides a good compromise between high and low frequency sensitivity.

[1]  Ricardo Garcia,et al.  Compositional mapping of surfaces in atomic force microscopy by excitation of the second normal mode of the microcantilever , 2004 .

[2]  Ute Rabe,et al.  Acoustic microscopy by atomic force microscopy , 1994 .

[3]  Georg Schitter,et al.  State-space model of freely vibrating and surface-coupled cantilever dynamics in atomic force microscopy , 2004 .

[4]  Paul K. Hansma,et al.  Characterization and optimization of the detection sensitivity of an atomic force microscope for small cantilevers , 1998 .

[5]  Tilman E. Schäffer,et al.  Force spectroscopy with a large dynamic range using small cantilevers and an array detector , 2002 .

[6]  Jan Greve,et al.  A detailed analysis of the optical beam deflection technique for use in atomic force microscopy , 1992 .

[7]  Robert W. Stark,et al.  Higher harmonics imaging in tapping-mode atomic-force microscopy , 2003 .

[8]  Martin Stark,et al.  Inverting dynamic force microscopy: From signals to time-resolved interaction forces , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[9]  Martin Stark,et al.  Higher-harmonics generation in tapping-mode atomic-force microscopy: Insights into the tip–sample interaction , 2000 .

[10]  R. Clough,et al.  Dynamics Of Structures , 1975 .

[11]  M. Gustafsson,et al.  Scanning force microscope springs optimized for optical‐beam deflection and with tips made by controlled fracture , 1994 .

[12]  R. Williams,et al.  Imaging the elastic nanostructure of Ge islands by ultrasonic force microscopy , 1998 .