Initial stages of the contact between a metallic tip and carbon nanotubes

We present an experimental and theoretical study of the interaction between a tip and single-walled carbon nanotubes (SWCNT) lying on a SiO2 surface. Adhesion and jump-to-contact forces (JC) are measured in a high vacuum system for SWCNT with diameters (D) ranging from 1.4 to 4.5 nm; we find adhesion forces approximately 3.2 nN and JC forces approximately 2.4 nN. Simulations yield adhesion forces in agreement with experiment showing that for D approximately 1.4 nm half of this force is due to tip-SWCNT and tip-SiO2 van der Waals interactions.