Mechanisms of Single-Walled Carbon Nanotube Probe−Sample Multistability in Tapping Mode AFM Imaging

Peeling of Long, Straight Carbon Nanotubes from Surfaces

The adhesion of long, straight, single-walled carbon nanotubes to surfaces is examined using multidimensional force spectroscopy. We observed characteristic signatures in the deflection and frequency response of the cantilever indicative of nanotube buckling and slip-stick motion as a result of compression and subsequent adhesion and peeling of the nanotube from the surface. The spring constant and the elastic modulus of the SWNT were estimated from the frequency shifts under tension. Using elastica modeling for postbuckled columns, we have determined the static coefficient of friction for the SWNT on alkanethiol-modified gold surfaces and showed that it varies with the identity of the monolayer terminal group.

Investigation of the carbon nanotube AFM tip contacts: free sliding versus pinned contact

Mechanical response of carbon nanotube atomic force microscope probes are investigated using a thermal noise forcing. Thermal noise spectra are able to investigate mechanical behaviors that cannot be studied using classical atomic force microscope modes. Experimental results show that the carbon nanotube contacts can be classified in two categories: the free sliding and pinned cases. The pinned contact case requires the description of the cantilever flexural vibrations with support spring-coupled cantilever boundary conditions. Our experimental results show that carbon nanotubes exhibit different contact behaviors with a surface, and in turn different mechanical responses.

Carbon nanotube tips for atomic force microscopy

The development of atomic force microscopy (AFM) over the past 20 years has had a major impact on materials science, surface science and various areas of biology, and it is now a routine imaging tool for the structural characterization of surfaces. The lateral resolution in AFM is governed by the shape of the tip and the geometry of the apex at the end of the tip. Conventional microfabrication routes result in pyramid-shaped tips, and the radius of curvature at the apex is typically less than 10 nm. As well as producing smaller tips, AFM researchers want to develop tips that last longer, provide faithful representations of complex surface topographies, and are mechanically non-invasive. Carbon nanotubes have demonstrated considerable potential as AFM tips but they are still not widely adopted. This review traces the history of carbon nanotube tips for AFM, the applications of these tips and research to improve their performance.

Amplitude response of single-wall carbon nanotube probes during tapping mode atomic force microscopy: Modeling and experiment

Imaging of surfaces with carbon nanotube probes in tapping mode results frequently in complex behavior in the amplitude-distance curves monitored. Using molecular mechanics simulations, we calculate the force exerted on a nanotube pressed against a smooth surface as it undergoes deformation and buckling. This nonlinear force is then used in a macroscopic equation, describing the response of a damped harmonic oscillator, to predict the amplitude response of a nanotube AFM probe. Similarities between the prediction and experiment suggest that the complex amplitude response seen in the experiment may be explained by the nonlinearity in the force exerted on the nanotube and thus must not necessarily be related to the structure of the surface.