Sophie Marsaudon

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.

Analysis of mechanical properties of single wall carbon nanotubes fixed at a tip apex by atomic force microscopy

An investigation of the mechanical properties of single wall carbon nanotubes (SWNT) fixed at a tip apex was performed using a frequency modulation-atomic force microscope (FM-AFM). The FM-AFM method allows the measurement of conservative and non-conservative forces separately and unambiguously. The FM-AFM analysis provides information that aids the understanding of the effects of the interaction between the free SWNT end and the surface: the resonant frequency shifts provide information on the effective SWNT spring constant, while the damping signal gives information on the type of contact between the tube and the surface. The variation of the damping signal as a function of the tip surface distance shows that the additional energy loss produced by the interaction between the tube and the surface is mostly due to an adhesion hysteresis. As a result, the increase of the damping signal is correlated to the existence of intermittent contact situations. The whole variations show how the contact between the free SWNT end and the surface modifies the elastic response of the tube.

Carbon nanotubes adhesion and nanomechanical behavior from peeling force spectroscopy

AbstractApplications based on single walled carbon nanotube (SWNT) are good example of the great need to continuously develop metrology methods in the field of nanotechnology. Contact and interface properties are key parameters that determine the efficiency of SWNT functionalized nanomaterials and nanodevices. In this work we have taken advantage of a good control of the SWNT growth processes at an atomic force microscope (AFM) tip apex and the use of a low noise (10−13 m/√Hz) AFM to investigate the mechanical behavior of a SWNT touching a surface. By simultaneously recording static and dynamic properties of SWNT, we show that the contact corresponds to a peeling geometry, and extract quantities such as adhesion energy per unit length, curvature and bending rigidity of the nanotube. A complete picture of the local shape of the SWNT and its mechanical behavior is provided.

Competition of elastic and adhesive properties of carbon nanotubes anchored to atomic force microscopy tips

In this paper we address the mechanical properties of carbon nanotubes anchored to atomic force microscopy (AFM) tips in a detailed analysis of experimental results and exhaustive description of a simple model. We show that volume elastic and surface adhesive forces both contribute to the dynamical AFM experimental signals. Their respective weights depend on the nanotube properties and on an experimental parameter: the oscillation amplitude. To quantify the elastic and adhesive contributions, a simple analytical model is used. It enables analytical expressions of the resonance frequency shift and dissipation that can be measured in the atomic force microscopy dynamical frequency modulation mode. It includes the nanotube adhesive contribution to the frequency shift. Experimental data for single-wall and multi-wall carbon nanotubes compare well to the model predictions for different oscillation amplitudes. Three parameters can be extracted: the distance necessary to unstick the nanotube from the surface and two spring constants corresponding to tube compression and to the elastic force required to overcome the adhesion force.

Experimental determination of conservative and dissipative parts in the tapping mode on a grafted layer: comparison with frequency modulation data

The aim of the present work is to extract the conservative and dissipative parts of the tip–sample interaction from the atomic force microscope amplitude modulation mode (AM, often called tapping). To do so, analytical expressions are used to transform the experimental amplitudes and phase variations with tip–sample distance to frequency shift and damping coefficient. The experimental procedure for the separation is detailed. The separated conservative and dissipative parts from the AM mode are compared for two driving frequencies, and then they are compared to the frequency modulation mode (FM, often called resonant non-contact) measurements for two different amplitudes. The conservative parts from the AM measurements are similar to the frequency shifts measured in the FM mode and also the dissipative parts from the AM measurements are very close to the dissipation measured in the FM mode. Experimentally, this good agreement is related to the small amplitude variation in the AM data on a chemically controlled grafted layer. Those results show experimentally that the AM and FM modes are just two different ways to probe the same tip–sample interaction. They also validate the AM data treatment to separate the conservative and dissipative parts as the only hypothesis needed is that only the fundamental harmonic contributes to the signal.

Drying nano particles solution on an oscillating tip at an air liquid interface: what we can learn, what we can do

Evaporation of fluid at micro and nanometer scale may be used to self-assemble nanometre-sized particles in suspension. Evaporating process can be used to gently control flow in micro and nanofluidics, thus providing a potential mean to design a fine pattern onto a surface or to functionalize a nanoprobe tip. In this paper, we present an original experimental approach to explore this open and rather virgin domain. We use an oscillating tip at an air liquid interface with a controlled dipping depth of the tip within the range of the micrometer. Also, very small dipping depths of a few ten nanometers were achieved with multi walls carbon nanotubes glued at the tip apex. The liquid is an aqueous solution of functionalized nanoparticles diluted in water. Evaporation of water is the driving force determining the arrangement of nanoparticles on the tip. The results show various nanoparticles deposition patterns, from which the deposits can be classified in two categories. The type of deposit is shown to be strongly dependent on whether or not the triple line is pinned and of the peptide coating of the gold nanoparticle. In order to assess the classification, companion dynamical studies of nanomeniscus and related dissipation processes involved with thinning effects are presented.

Dynamic force microscopic study of a triblock copolymer with the AFM non contact resonant mode

We present an experimental study of a triblock copolymer with the AFM non contact resonant mode. This dynamic force microscope allows the attractive tip surface interaction to be finely tuned by varying the shift of the resonance frequency. The triblock copolymer chosen exhibits a periodic structure of lamellae with different mechanical properties. Height and dissipation images are recorded at different resonance frequency shifts. The dissipation images show the influence both of the strength of the attractive interaction and of the mechanical properties onto the contrast. In addition a comparative study between Tapping and dissipation images is performed, reverse contrast observed is explained as a direct consequence of the intrinsic mechanical properties of each lamella.

Carbon Nanotubes as SPM Tips: Mechanical Properties of Nanotube Tips and Imaging

In this chapter, a thorough investigation of the use of carbon nanotubes as nanoprobes of an atomic forcemicroscope is presented. Because of theirmechanical robustness, their controlled geometry with high aspect ratio, their small size and well-defined chemical composition, carbon nanotubes as probes solve many experimental and modeling problems of local probes methods. Over the last decade, many attempts were dedicated to use of carbon nanotubes as nanoprobes. However, in spite of a large number of works, there are still many questions concerning the proper use of carbon nanotubes, such as the type of more appropriate growth methods and an accurate interpretation of the mechanical properties. We present two growth methods based on chemical vapor deposition: (1) anchoring of multiwalled nanotubes to a commercial Si tip and (2) direct growth of a single-walled nanotube on the tip apex. Control parameters such as radius, length, angle with the sample and anchoring are discussed. The mechanical properties of those nanotubes anchored to the tip aremodeled and experimentally probed by dynamical atomic force microscopy in frequency modulation mode. Most of the nanotube mechanical behavior can be understood with a flexural elasticity and an adhesive force. We particularly focus on evaluation of the nanotube equivalent stiffness and on its adhesion force and energy. We demonstrate that the balance between adhesion and elastic energy can be altered by changing the oscillation amplitude. Finally, the nanotube adhesion to the surface is used to image a heterogeneous sample, demonstrating the ability of the nanotube to be chemically sensitive.

High yield grafting of carbon nanotube on ultra-sharp silicon nanotips: Mechanical characterization and AFM imaging

The novelty of this work lies in the fabrication of nanotips without any facet allowing the high yield of robust carbon nanotube (CNT) grafting for atomic force microscopy (AFM) experiments.