Mechanical properties of a carbon nanotube fixed at a tip apex:: A frequency-modulated atomic force microscopy study -: art. no. 035445

An investigation of mechanical properties of carbon nanotubes (CNTs) fixed at a tip apex was performed using a frequency modulation-atomic force microscope (FM-AFM). The FM-AFM method allows to measure conservative and nonconservative forces separately and unambiguously. The force gradient analysis provides a good understanding of the effects of the interaction between the free CNT end and the surface; the resonant frequency shifts provide information on the effective CNT spring constant, while the damping signal gives information on the sticking condition of the tube on the surface. Variation of the damping signal indicates that additional energy losses are mostly due to adhesion hysteresis. In particular, a close correlation between damping and resonant frequency shifts was observed. The whole variations show how the contact between the free CNT end and the surface modifies the elastic response of the tube and, in turn, the resonant frequency shift. Although not being quantitative, the cumulate variations of damping and resonance frequency provide a picture that is accurate enough to explain the effect for imaging and, in turn, find routes to enhance the contrast. An example is given with an image of InAs nanodots on GaAs.