Investigation of the interaction between carbon nanotube tip and silicon sample through molecular dynamic simulation

Atomic Force Microscopy (AFM) has become a standard tool in experimental surface metrology, revealing atomic scale features of the surfaces. Carbon nanotube represents ideal structure for AFM tips because of their tiny diameter, high aspect ratio and high strength. This article employs molecular dynamics (MD) simulation approach to investigate the atomic-scale interaction between the AFM tips represented by carbon nanotube and sample. The interaction force between two different types of single walled carbon nanotube (SWCNT) tips including open ended carbon nanotube and capped carbon nanotube while the deformation mechanism during the measurement was discussed in detail. Firstly, the interaction force between SWCNT tips and sample in contact mode was simulated by using hybrid potential. The stiffness of the two different types of single walled carbon nanotubes were verified. The simulation results indicate that capped SWCNT tip is more prone to tilt than open ended SWCNT tip, but the ability to resist deformation is stronger. Then the dynamic model of tip-sample system in tapping mode was established. The relationship between the tip of load and the distance in the process of approaching to the sample was obtained by curve fitting. The numerical solution was achieved by solving the dynamic equation and frequency spectrum was obtained with the method of Fourier transforms.