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

Imaging of aromatic molecules by tuning-fork based LT-NC-AFM
P.II-02
Bartosz Such 1 , Thilo Glatzel 1 , Shigeki Kawai 1 , Sacha Koch 1 , Alexis Baratoff 1 , Ernst
Meyer 1 , Catelijne H. M. Amijs 2 , Paula de Mendoza 2 , and Antonio M. Echavarren 2
1 Department of Physics, University of Basel, Kilngelbergstrasse 82, 4056 Basel, Switzerland
2 Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona, Spain.
Utilizing tuning forks [1,2] as sensors for NC-AFM allowed for extending
capability of the technique to cryogenic temperatures.
In the presentation, high resolution imaging of large aromatic molecules at 5K will
be presented. Functionalized truxeses (10,15-dihydro-5H-diindeno[1,2-a;1',2'c]fluorine)
with three 4-cyanobenzyl groups added in positions 5, 10, and 15 in a syn relative
configuration have been evaporated onto a clean Cu(111) surface. The molecules adopt
planar configuration and form a triangular network (see fig. 1). However, the
cyanobenzyl groups are flexible and can adopt various configurations for neighbouring
molecules. Supposedly the cyanobenzyl groups standing in the upright position appear in
frequency shift images as dark spots (areas of larger interaction) due to enhanced
electrostatic interaction with the tip, proving NC-AFM capability of imaging internal
structures of aromatic molecules.
Figure 1: 7.8x7.8 nm constant height image of truxene layer on Cu(111) surface. a) current (tip
bias = -1.8 V, colour scale form 173 pA to 503 pA); b) frequency shift, Ap-p = 260 pm f0 = 26417,
Q = 47000, colour scale from -56.5 Hz to -34.8 Hz.
[1] F.J. Giessibl, Appl. Phys. Lett. 76, 1470 (2000).
[2] M. Ternes et al. Science 319, 5866 (2008).
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