Characterization of Mechanical Properties of Suspended Carbon Nanotubes in Liquid

Abstract

In this paper, we describe the mechanical interaction between the vibrating tip of an atomic force microscope (AFM) and carbon nanotubes (CNTs) suspended over a trench on a Si wafer. The interaction was detected by recording the oscillation amplitudes of the cantilever tip above the suspended CNTs during both tip-down and tip-up processes. We refer to the oscillation amplitude versus tip vertical position as a force curve. In the force curve obtained in air, the mechanical response of a CNT bundle under a periodic external force applied by the tip is interpreted as a simple model that includes the attachment/ detachment of the CNTs onto the tip surface and the oscillation of the CNTs fixed to the tip. The curve obtained in water has features similar to that obtained in air. The difference between the force curves obtained in air and in water suggests that the adhesion force between the AFM tip and CNTs is weaked in water than in air.

Photocurrent properties of freely suspended carbon nanotubes under uniaxial strain

“…[2] Furthermore, electric fields at the Schottky contacts between CNTs and metal contacts can separate optically excited electron-hole pairs, causing a photocurrent across electrically contacted CNTs. [5]- [7] At the same time, the electro-mechanical properties of CNTs have been studied both by locally manipulating CNTs with the tip of an atomic force microscope (AFM), [12]- [14] and by applying uniaxial [15]- [18] and torsional [19], [20] strain to the CNTs. Theorists have modeled the electronic behavior of the mechanically deformed CNTs by an enhanced electronic scattering at defects, [13], [21], [22] a structural induced alteration of the CNTs' band gap, [15]- [19], [21], [23]- [25], [29] and by a mechanical induced transition from sp 2 to sp 3 hybridization of the carbon bonds.…”

Observation of Suspended Carbon Nanotube Configurations Using an Atomic Force Microscopy Tip

“…In the latter model, an abrupt change in the AD curve should be observed, as observed in our previous experiment in water. 27) In the case of Fig. 3, therefore, a slip at the interface between the CNTs and the substrate surface is considered to be the main reason for the observed increase in the tip-up process.…”

“…25,26) In a previous study, we reported that various phenomena of suspended CNTs, such as an oscillation with an AFM tip in the tapping mode, can be detected by a change in the amplitude of the oscillating tip. 27) We also obtained interactive forces at a CNT/CNT interface, a CNT/substrate interface, and a CNT/AFM tip interface in air and in pure water using this technique, and found that the forces in water are much different from those in air.…”