Dynamic force spectroscopy using cantilever higher flexural modes

By means of force spectroscopy measurements performed with the cantilever first and second flexural modes under the frequency modulation detection method, the authors corroborate the validity of the relation between tip-surface interaction force and frequency shift for force spectroscopy acquisition using higher cantilever eigenmodes. They estimate a cantilever effective stiffness for the second eigenmode 73 times larger than the static stiffness. This large effective stiffness enables them to perform force spectroscopy with a cantilever oscillation amplitude (A(0)) as small as 3.6 A. The authors provide experimental evidence that, at such small A(0) values, normalized frequency shift curves deviate from a A(0)(3/2) scaling and the signal-to-noise ratio is considerably enhanced.