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

Contacting self-ordered molecular wires by
nanostencil lithography
L. Gross, R.R. Schlittler, and G. Meyer
IBM Research, Zurich Research Laboratory, 8803 Rüschlikon, Switzerland
Th. Glatzel, S. Kawai, S. Koch, and E. Meyer
Department of Physics, University of Basel, 4056 Basel, Switzerland.
P.I-36
We grew self-ordered cyanoporphyrin molecular wires [1] on thin epitaxial NaCl(100)
layers on top of GaAs substrates under UHV conditions. This molecular assemblies form
one- and two-dimensional wires with a length of several 10nm depending on the substrate
conditions. Using a shadow masking technique [2], a nanostencil combined with a room
temperature nc-AFM in UHV, we additionally evaporate Au and Cr electrodes with a
thickness of around 3nm in situ. The resulting combined molecular and metal structures
are investigated by means of nc-AFM and KPFM (Kelvin probe force microscopy).
While nc-AFM enabled us to control the tip sample distance on the very complex and
partly insulating surface, KPFM has been used to determine and compensate changes of
the local contact potential difference (LCPD).
Figure 1: (a) nc-AFM image (size 1.7um x 1.7um, LCPD compensated) of NaCl/GaAs covered
with cyanoporphyrin molecular wires and clusters. A Cr electrode was evaporated through a
stencil mask in order to contact molecular wires. b) Simultaneously measured LCPD of the
structure.
[1] Th. Glatzel, L. Zimmerli, S. Koch, S. Kawai, and E. Meyer, Appl. Phys. Lett. 94, 063303 (2009).
[2] P. Zahl, M. Bammerlin, G. Meyer, and R. R. Schlittler, Rev. Sci. Instrum. 76, 023707 (2005).
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