Analysis of mechanical properties of single wall carbon nanotubes fixed at a tip apex by atomic force microscopy

An investigation of the mechanical properties of single wall carbon nanotubes (SWNT) fixed at a tip apex was performed using a frequency modulation-atomic force microscope (FM-AFM). The FM-AFM method allows the measurement of conservative and non-conservative forces separately and unambiguously. The FM-AFM analysis provides information that aids the understanding of the effects of the interaction between the free SWNT end and the surface: the resonant frequency shifts provide information on the effective SWNT spring constant, while the damping signal gives information on the type of contact between the tube and the surface. The variation of the damping signal as a function of the tip surface distance shows that the additional energy loss produced by the interaction between the tube and the surface is mostly due to an adhesion hysteresis. As a result, the increase of the damping signal is correlated to the existence of intermittent contact situations. The whole variations show how the contact between the free SWNT end and the surface modifies the elastic response of the tube.