Complex dynamics of carbon nanotube probe tips.

Carbon nanotube (CNT) tips in tapping mode atomic force microscopy (AFM) enable very high-resolution imaging, measurements, and manipulation at the nanoscale. We present recent results based on experimental analysis that yield new insights into the dynamics of CNT probe tips in tapping mode AFM. Experimental measurements are presented of the frequency response and dynamic amplitude-distance data of a high-aspect-ratio multi-walled (MW) CNT tip. Higher harmonics of the microcantilever are measured in frequency ranges corresponding to attractive regime and the repulsive regime where the CNT buckles dynamically. Surface scanning is performed using a MWCNT tip on a SiO(2) grating to verify the imaging instabilities associated with MWCNT buckling when used with normal control schemes in the tapping mode. Lastly, the choice of optimal setpoints for tapping mode control using CNT tip are discussed using the experimental results.