[Back]

M. Wagner, J. Hofinger, M. Setvin, L. Boatner, M. Schmid, U. Diebold:
"Prototypical Organic-Oxide Interface: Intramolecular Resolution of Sexiphenyl on In₂O₃(111)";
ACS Applied Materials & Interfaces, 10 (2018), 14175 - 14182.

Prototypical Organic
−
Oxide Interface: Intramolecular Resolution of
Sexiphenyl on In
2
O
3
(111)
Margareta Wagner,
*
,
+
Jakob Ho
fi
nger,
+
Martin Setv
í
n,
+
Lynn A. Boatner,
#
Michael Schmid,
+
and Ulrike Diebold
+
+
Institute of Applied Physics, TU Wien, Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria
#
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
*
S
Supporting Information
ABSTRACT:
The performance of an organic semiconductor
device is critically determined by the geometric alignment,
orientation, and ordering of the organic molecules. Although
an organic multilayer eventually adopts the crystal structure of
the organic material, the alignment and con
fi
guration at the
interface with the substrate/electrode material are essential for
charge injection into the organic layer. This work focuses on
the prototypical organic semiconductor para-sexiphenyl (6P)
adsorbed on In
2
O
3
(111), the thermodynamically most stable
surface of the material that the most common transparent
conducting oxide, indium tin oxide, is based on. The onset of
nucleation and formation of the
fi
rst monolayer are followed with atomically resolved scanning tunneling microscopy and
noncontact atomic force microscopy (nc-AFM). Annealing to 200
°
C provides su
ffi
cient thermal energy for the molecules to
orient themselves along the high-symmetry directions of the surface, leading to a single adsorption site. The AFM data suggests
an essentially planar adsorption geometry. With increasing coverage, the 6P molecules
fi
rst form a loose network with a poor
long-range order. Eventually, the molecules reorient into an ordered monolayer. This
fi
rst monolayer has a densely packed, well-
ordered (2
×
1) structure with one 6P per In
2
O
3
(111) substrate unit cell, that is, a molecular density of 5.64
×
10
13
cm
−
2
.

indium oxide, sexiphenyl, organic molecules, atomic force microscopy, scanning tunneling microscopy, adsorption site, monolayer