Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)


Accueil > La Recherche > Axes & Equipes > Nanostructures & Spectroscopies > Equipe : Nanomatériaux > Thème : Propriétés intrinsèques des nanotubes individuels et du graphène

Scanning probe microscopy studies on individual single-walled carbon nanotubes

par Sébastien LAYSSAC - publié le

Involved researchers : T. Michel, M. Paillet, R. Parret, A. Zahab
Collaborations : P. Poncharal (LPMCN, Lyon), J. C. Meyer (MPI Stuttgart, Germany), Z. Wang (EMPA, Switzerland)

For investigations at the single nanotube level, we are using the broad possibilities offered by the local probe microscopy in different fields like electrostatics, mechanics, magnetic, solid state electronics and functionalization chemistry.
We have developed experimental skills in AFM imaging and manipulation of nanosized objects such as nanoparticles and carbon nanotubes. This enables various studies such as :
- nanotube sample diameter distribution measurements
- investigation of the nanotube growth mechanism
- making the evidence of a molecular linkage between two nanotubes after chemical functionnalization by AFM manipulation
- measurements of the SWNT radial deformation due to van der Waals forces between nanotube and silica substrate.

Figure 1 : Right, diameter statistics of a typical CVD nanotube sample as measured by AFM and HRTEM. Left, same sample area before (a) and after (b) nanotube growth. The arrow points the catalyst nanoparticle that nucleates the nanotube.The fact that the nanoparticle is not moving during the nanotube growth validates the "based growth" model as the one involved here - © L2C

We provided the first EFM experimental confirmation that charged carbon nanotubes exhibit charge amount and distribution governed by classical electrostatics. From our experiments, we conclude that charges are distributed uniformly along the nanotubes. We demonstrate that electrostatic force microscopy can accurately measure the amount of charges per unit length. We found that this amount is diameter dependent and in the range of 1 electron per nanometer for a 2.5 nm nanotube at a potential of -3,5V.

Figure 2 : (a) AFM topography image of an individual SWNT. (b), (c) EFM images recorded at VEFM -4 and +4 V, respectively, before charging of the nanotube. (d),(e) EFM images recorded at VEFM -4 and +4 V, respectively, after charging of the nanotube at 5 V for 30 s. Insert, picture of the experimental set-up which is an AFM enclosed in a glove box to ensure reduced humidity during electrostatic measurements - © L2C

Figure 3 : Left part, EFM images of a charged nanotube network measured with opposite tip potentials. Right, linear density of electrical charges vs nanotube diameter as measured by EFM on this network. Solid line : calculated values with typical classical electrostatics. To determine the charge amount, we used the plane-plane capacitor model. The conductive tip motion is sensitive to the gradient of the force in the vertical direction (z), which is proportional to the second derivative of the tip to sample capacitance C(z) - © L2C

M. Holzinger et al., Carbon 42, 941 (2004). M. Paillet et al., J. Phys. Chem. B 108, 17112 (2004). M. Paillet, et al., PRL 94, 186801 (2005), M. Paillet, Thèse de l’Université Montpellier 2 (2005), V. Jourdain et al., J. Phys Chem. B 110, 9759 (2006).