Chemistry Reference
In-Depth Information
Figure 4.11. STM image of a SAM of cyclotrimeric terthiophenediacetylene on
HOPG.
V
t
=−
0
.
88 V,
I
t
=
50 pA: 10 nm
×
10 nm. Courtesy of Dr E. Mena-
Osteritz.
2001) with
17
. Examples of
coincident-IB
systems are perylene/Cu(110)
4
50
/
(Chen
et al.
, 2002), which exhibits eight-fold periodicity along the [110] azimuth
and incommensurate order along [001] and HBC/Au(111) (Sellam
et al.
, 2001)
with
.
The formation of MLs of organic molecules at the liquid/HOPG interface can be
in situ
characterized with a STM. Depending on the molecule-solvent combination
used, the MLs form spontaneously, giving rise to well-defined packings. HOPG
surfaces are extremely popular because they can be easily prepared by cleavage and
exhibit micrometre-sized terraces. However, because of the graphite basal plane,
substrate-overlayer
−
36
−
6
.
17 3
interactions are expected to strongly influence the packing
of the overlayer molecules. The solvent used plays an important role in stabilizing
the MLs.
Let us first explore the selected STM example concerning the molecular sys-
tem cyclotrimeric terthiophenediacetylene shown in Fig. 4.11 (Mena-Osteritz &
Bauerle, 2001). The synthesis of this molecule was discussed in Section 2.5
(Fig. 2.17). When a solution of the cyclotrimeric terthiophenediacetylene macrocy-
cle in C
6
H
3
Cl
3
is brought onto a freshly cleaved HOPG substrate, spontaneous for-
mation of a SAMis foundwith honeycomb ordering at the solution/HOPG interface.
π
−
π
