Plenarvorträge - DPG-Tagungen

Oberflächenphysik Donnerstag
into the respective phenomena, we have studied self-assembled monolayers
(SAMs) formed from terphenyl-substituted alkanethiols with varying
length of the alkyl part on (111) Au and Ag substrates. We used several
complementary experimental techniques such as X-ray photoelectron
spectroscopy (XPS), high-resolution XPS, near edge X-ray absorption
fine structure spectroscopy, infrared reflection absorption spectroscopy,
ellipsometry, and water contact angle measurements to characterize the
SAMs. Odd-even changes in the packing density and orientation of the
terphenyl moieties, etc have been observed and considered in detail. The
results imply a predominant role of the headgroup-substrate interaction
in the balance of structure-building forces in the aliphatic SAMs.
O 33.3 Do 11:45 H39
Using a focused soft X-ray beam for the characterization
and fabrication of monomolecular patterns — •Michael
Zharnikov 1 , Ruth Klauser 2 , Anne Paul 1 , Armin Gölzhäuser 1 ,
S.-C. Wang 2 , I.-H. Hong 2 , and Michael Grunze 1 — 1 Angewandte
Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany
— 2 National Synchrotron Radiation Research Center, Hsinchu
30077, Taiwan (ROC)
We have utilized scanning soft X-ray photoelectron spectromicroscopy
to image and characterize different electron-beam patterned selfassembled
monolayers (SAMs) on gold substrates. The lateral structures
in all SAM-based patterns could be clearly distinguished. The irradiated
areas generally revealed a smaller Au 4f intensity and a higher C1s intensity
than non-irradiated ones due to the adsorption of airborne carboncontaining
molecules on more hydrophilic and rough irradiated areas.
Also, chemical changes in some of the resists could be directly monitored
as soon as the respective emissions were intense enough as compared to
the inelastic background. In addition, we found that the highly intense
zone-plate-focused soft X-ray beam can cause non-intentional irradiationinduced
modification of the SAMs during the SPEM image acquisition.
Taking advantage of this phenomenon, we demonstrate that the X-ray microprobe
can be utilized for in-situ surface patterning of the monomolecular
SAM resist with subsequent imaging of the fabricated patterns.
O 33.4 Do 12:00 H39
Electron-vibron coupling in the NEXAFS spectra of large organic
molecules — •Dominique Hübner 1 , A. Schöll 1 , R. Fink 2 ,
K.C. Prince 3 , R. Richter 3 , S. Stranges 4 , and E. Umbach 1 —
1 Univ. Würzburg, Exp. Phys. II — 2 Univ. Erlangen, Phys. Chem. II —
3 Sincrotrone Trieste — 4 CNR-Istituto di Metodologie Inorganiche e dei
Plasmi
High-resolution NEXAFS spectroscopy is ideally suited to investigate
the electronic structure of large organic molecules in both, the
condensed and the gas phase. In ideal cases one observes distinct fine
structures which are attributed to the electron vibron coupling. Astonishingly,
the electronic excitations significantly couple to few vibronic
states. We present NEXAFS data on the heteroaromatic molecule acenaphthenequinone
(ANQ). ANQ is at present the largest molecule for
which vibronic fine structure has been observed for O K-edge excitations.
Remarkably, the O K-edge spectra of the condensed and gas phase
hardly differ. The well-resolved data furthermore allow to describe the
anharmonicity of the excited state potential. Whereas there are no differences
for O 1s excitations, the comparison for the C K-edge for the
condensed and gas phase gives clear hints that the π-interactions between
neighboring molecules mostly involves the aromatic core. The project is
financed by BMBF under contract 05 KS1 WWA/5.
O 33.5 Do 12:15 H39
Effects of the molecular electric dipole on the HOMO-band
fine structure: metal-phthalocyanine on graphite — •Satoshi
Kera 1,2 , Hiroyuki Yamane 3 , and Nobuo Ueno 3 — 1 Exp. Phys. II,
Univ. Würzburg, Am Hubland, 97074 Würzburg — 2 Institute for Molecular
Science, Okazaki 444-8585, Japan — 3 Chiba Univ., Inage-ku, Chiba
263-8522, Japan
Photoelectron fine structures were observed for metal-phthalocyanine
(Pb-, and OTiPc) ultrathin films on HOPG. They have an electric dipole
perpendicular to the π-conjugated plane, hence a well-defined dipole layer
could be intentionally produced by preparing an oriented monolayer. For
the OTiPc film with asgrown island, in which staggered doublelayers are
formed, we observed two prominent peaks for the HOMO band (single
π state) originating from different molecular orientations in the islands.
Upon annealing, they form a uniform monolayer with the O atom protruding
into the vacuum, and give an unusually sharp HOMO band [1].
The EB difference of the HOMO bands between the staggered doublelayer
and the oriented monolayer was found to agree with the Evac shift, leading
to the conclusion that the relative position of the molecular energy
level with respect to the substrate EF can be changed due to the dipole
layer. These results suggest that we can tailor device interface properties
by controlling the direction and/or the magnitude of the molecular electric
dipole. Moreover it is also interesting to discuss the origins of the
HOMO-bandwidth at the organic/inorganic interfaces. [1] S. Kera et al,
Chem. Phys. Lett. 364, 93 (2002).
O 33.6 Do 12:30 H39
Preparation of submicron-structured alkylsiloxane monolayers
using prepatterned silicon substrates by laser direct writing —
•Nils Hartmann, Thorsten Balgar, and Eckart Hasselbrink
— Universität Duisburg-Essen, Fachbereich Chemie, Universitätsstr. 5,
45141 Essen
A new constructive method for the preparation of laterally structured
alkylsiloxane monolayers is demonstrated. Laser direct writing has been
used to create oxide patterns on H-terminated Si(100) samples under
ambient conditions. Depending on the laser power and the writing speed
oxide structures with a lateral resolution below 500 nm can be prepared
routinely. The patterned samples are suitable as temporary templates
for the preparation of laterally structured octadecylsiloxane monolayers.
Prior to immersion in an octadecyltrichlorosilane (OTS) solution,
however, a hydration of the samples in water is essential to facilitate a
selective coating of the oxidized areas. After coating, atomic force microscopy
(AFM) reveals the formation of octadecylsiloxane islands exclusively
along the oxide lines.
O 33.7 Do 12:45 H39
Epitaxy of titanyl phthalocyanine on Au(111) surfaces —
•Karsten Walzer, Stefan Mannsfeld, Holger Pröhl, Thomas
Dienel, Torsten Fritz, and Karl Leo — Institut für Angewandte
Photophysik, TU Dresden, 01062 Dresden
Organic molecular beam epitaxy (OMBE) was applied to grow titanyl
phthalocyanine (TiOPc) thin films on a Au(111) single crystalline surface
in UHV. The growth was monitored by differential reflection spectroscopy
(DRS) in situ, yielding data for submonolayer up to multilayer coverage.
Using STM and LEED, we studied the epitaxial growth behaviour. We
observed both well-ordered 2d structures and the formation of 3d densely
packed crystals. The dimension of the unit mesh in the monolayer regime
was obtained from LEED measurements. From the structural data and
subsequently performed simulations we conclude that the orientation of
the domains in the first monolayer is determined by the substrate lattice.
In some cases also the intramolecular structure was resolved by STM.
We found that especially in small vacancies of the monolayer often one
molecule is confined, which appears rotated (in-plane) with respect to
the surrounding phthalocyanine molecules.