Noncontact Atomic Force Microscopy - Yale School of Engineering ...

We-1200
Atomic-Resolution Damping Force Spectroscopy on Nanotube Peapods
with Different Tube Diameters
M. Ashino 1 , R. Wiesendanger 1 , A. N. Khlobystov 2 , S. Berber 3,4 , and D. Tománek 4
1 Inst. of Applied Physics & Microstructure Research Center, University of Hamburg, Hamburg, Germany
2 School of Chemistry, University of Nottingham, Nottingham, UK
3 Physics Department, Gebze Institute of Technology, Gebze, Turkey
4 Physics and Astronomy Department, Michigan State University, East Lansing, USA.
Damping of the oscillating cantilever in dynamic atomic force microscopy (AFM)
includes valuable information about the local vibrational structure and elastic compliance
of the samples. We present atomically-resolved maps of damping in nanotube peapods,
showing their capability of identifying the presence and location of encapsulated Dy@C82
metallofullerenes as well as their packing structure in the different diameters of carbon
nanotubes. In our study, the physical origin of damping is elucidated in a microscopic
model, and its relationship to the outer tube diameter is quantitatively interpreted by
calculating the vibrational spectrum and energy dissipation in peapods with different
diameters using ab initio total energy and molecular dynamics calculations [1].
In our experiment we probed sparsely deposited (Dy@C82)@SWNT peapods on insulating
oxide layers of a Si substrate by dynamic AFM under constant oscillation amplitude conditions in
ultrahigh vacuum (p≈10 -8 Pa) and at low temperature (T≈13 K). As seen in Fig. 1(a), the
atomically site-specific damping signal is obviously detected over the peapod. Besides,
Figure 1(b) shows that its maximum energy is closely related to the enclosing nanotube
diameter d, determined on the basis of the simultaneously observed topographic images.
(a) (b)
Figure 1: (a) Simultaneously obtained dynamic AFM topography (left) and damping (right)
images of an empty SWNT (1,3) and a (Dy@C82)@SWNT peapod (2,4) with the same outer
tube diameter d≈1.62 nm. (b) Relationship between outer tube diameter d and the maximum
damping energy ΔEmax.
[1] M. Ashino, R. Wiesendanger, A. N. Khlobystov, S. Berber, and D. Tománek,
submitted for publication.
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