ENHANCED SENSITIVITY TO FORCE GRADIENTS BY USING HIGHER FLEXURAL MODES OF THE ATOMIC-FORCE MICROSCOPE CANTILEVER

Higher flexural modes of a Si cantilever are used in order to increase the operating frequencies in non-contact mode scanning force microsco py. By recording frequency responses at different tip-sample distances and by using different flexural modes, long-range tip-sample interact ions are studied. The experimental results reveal that operating at hi gher resonant modes makes it possible to improve sensitivity to force gradients and to avoid overlap between hydrodynamic interactions and a ttractive interactions in the range of 100-nm tip-sample distances. Us ing the second-harmonic, a sevenfold-enhanced sensitivity is demonstra ted. Finally, discussion on the appropriate technique related to force gradient measurement, i.e. slope detection or frequency modulation te chnique, is reported.