Adhesion energy of single wall carbon nanotube loops on various substrates

Abstract

International audienceThe physics of adhesion of one-dimensional nano structures such as nanotubes, nano wires, and biopolymers on different substrates is of great interest for the study of biological adhesion and the development of nano electronics and nano mechanics. In this paper, we present force spectroscopy experiments of individual single wall carbon nanotube loops using a home-made interferometric atomic force microscope. Characteristic force plateaus during the peeling process allow the quantitative measurement of the adhesion energy per unit length on various substrates: graphite, mica, platinum, gold, and silicon. Moreover, using a time-frequency analysis of the deflection of the cantilever, we estimate the dynamic stiffness of the contact, providing more information on the nanotube configurations and its intrinsic mechanical properties

Dynamic stiffness of the contact between a carbon nanotube and a flat substrate in a peeling geometry

“…approach and retraction, with a plateau-like behavior of the force during retraction: this is the signature of an adhesion and peeling process of the nanotube on the surface 13,14 . The steep evolution at the largest compression corresponds to a hard contact between the AFM tip and the substrate, while the jumps between different plateaus during retraction are the signatures of defects in the nanotube.…”

“…CNTs grow everywhere on the cantilever, and around 1 in 3 cantilevers has a CNT at the tip 14 . A typical sample is shown by the SEM (Scanning Electron Microscopy) image of figure 1(a).…”

“…With the hypothesis that the horizontal forces acting on the nanotube are negligible, we can also compute the vertical force acting on the nanotube 13,14 :…”

“…These peeling experiments are however restricted to the quasi-static mechanical behavior of the contact, since the time scales probed are of the order 1 s. In this article, we explore the dynamic response of the contact, which can be quite different. Indeed, in previous works 13, 14 , we showed that at frequencies higher than 10 kHz, the adhesion processes can be considered as frozen: the nanotube a) Electronic mail: ludovic.bellon@ens-lyon.fr has no time to adhere to (or detach from) the substrate, leading to a dynamic stiffness which is greater than the static one. We are therefore interested in probing the intermediate frequency range: does any characteristic time scale govern this dynamic behavior ?…”

“…For example, the AFM has been successfully used to characterize the adhesion of one dimensional nano-object, such as carbon nanotubes [3][4][5][6] . In particular, in peeling experiments, one measures the force while the nanotube is pulled from a flat substrate [7][8][9][10][11][12][13][14] . The force versus distance curve displays a signature specific to this peeling process, and can be used to extract the energy of adhesion between the nano-object and the surface.…”