Sensitivity Analysis of Carbon Nanotube Characteristics on Dynamic Behavior of Tapping-Mode Atomic Force Microscopy

Atomic force microscopy with attached carbon nanotube is an ideal tool in nano scale imaging, for its high precision caused by small tip diameter and high flexibility of carbon nanotube. In this paper sensitivity analysis of a tapping-mode atomic force microscopy (AFM) with large aspect ratio carbon nanotubes (CNT) probe tips is investigated. A finite-element method is used for vibration analysis of a continuous beam model of an AFM cantilever and vibration amplitude is extracted in different excitation frequencies and different tip separations from sample surface and the effect of nanotube characteristics such as its length, bending stiffness & tilt angle on dynamic behavior of AFM is examined. The results show that decreasing the CNT length or increasing the CNT bending stiffness or the number of CNT layouts, increases the resonance frequency, but its effect is small. The results also show that using stiffer nanotubes removes the possibility of buckling in the range of the frequencies close the natural frequency of the cantilever. This can cause more stability due to less buckling. Sensitivity analysis helps better choosing of the carbon nanotube characteristics.