Plenarvorträge - DPG-Tagungen

Symposium Organic and Hybrid Systems for Future Electronics Donnerstag
scale low-cost electronic devices has lead to intensive research. Pentacene
and Diindenoperylene (DIP) thin films on SiO2 are two prominent systems
due to their high structural order out-of-plane. While bottom contact
FET structures can be realized easily, preparation of top contacts
may involve diffusion of metal atoms (typically Au) deep into the organic
film changing its electronic properties. For a better understanding of the
growth process and the diffusion of noble metal atoms in crystalline organic
films, a radiotracer technique has been used to obtain diffusion
profiles and the condensation coefficient of noble metals for these films.
The results for Pentacene and DIP films will be presented with respect
to their structural properties and will be compared to polymer films.
SYOH 5.23 Do 18:00 B
Electronic Structure and Morphology of 7.8-Dimethylalloxazin
on Ag, Au, and HOPG — •Stefan Lach and Christiane Ziegler
— Erwin-Schrödinger-Str. 33 67663-Kaiserslautern
Our main emphasis was put on the investigation of the electronic and
structural behavior of thin films of the redox-active model substance
7.8-dimethylalloxazin (DMA) on several inorganic surfaces as a prerequisite
to construct organic/inorganic molecular electron transfer devices.
Alloxazines are capable of building up intermolecular hydrogen-bonded
complexes. The optimized structures of the monomer and several dimers
were calculated (DFT). The calculated eigenvalues were used to simulate
the theoretical photoelectron spectra of the monomer and the dimers.
Comparison of the calculations and simulations with the measured data
exhibit a small preference for a dimerization. Photoelectron spectroscopy
and morphology studies of ultra thin films from DMA on polycrystalline
silver and gold as well as on HOPG show distinct differences for these
substrates. On HOPG and Au there is no chemical interaction. On HOPG
a homogeneous, unstructured layer is formed, but on Au DMA shows island
growth with large islands and deep crevices in between. On Ag a
new state appears 1.2 eV below the Fermi level and smaller islands are
built on the substrate. A calculation and simulation of the photoelectron
spectra of a DMA/Ag-complex shows a good correspondence with the
experimental results.
SYOH 5.24 Do 18:00 B
Orientation of phthalocyanine thin films on disordered
substrates — •Heiko Peisert 1,2 , Indro Biswas 1 , Torsten
Schwieger 2 , Martin Knupfer 2 , Andreas Petr 2 , Lothar
Dunsch 2 , Danilo Dini 3 , Michael Hanack 3 , and Thomas Chasse 1
— 1 University of Tuebingen, IPC, Auf der Morgenstelle 8, 72076
Tuebingen, Germany — 2 Leibniz Institute for Solid State Research
Dresden, P.O. Box 270116, D-01171 Dresden, Germany — 3 University
of Tuebingen, Inst. Organ. Chem., Auf der Morgenstelle 18, D-72076
Tuebingen, Germany
We have studied the molecular orientation of fluorinated metallophthalocyanines
(CuPCFx with x = 0, 4, 16), and of tetra tert-butyl magnesium
phthalocyanine (MgPC(t-bu)4) on technically relevant organic
and inorganic substrates using polarisation-dependent x-ray absorption
spectroscopy. As organic substrate a mixture of poly-3,4-ethylenedioxythiophene
(PEDOT) and polystyrenesulfonate (PSS) was chosen, often
applied as electrode material in (all-)organic semiconductor devices. Although
we observe a chemical interaction at the PC/PEDOT:PSS interface
and a diffusion of Pc molecules into the polymer film [1], CuPcFx
grows in an ordered, ”standing” geometry on this substrate.
The tert-butyl metallophthalocyanines are highly soluble and thus they
are especially suitable for solution processed organic semiconductor thin
films. On polycrystalline gold evaporated MgPc(t-bu)4 molecules are as
highly ordered as CuPC. However, on Au(100) we observe a very high
orientation (the molecules lie) only for (sub-) monolayer coverages.
[1] H. Peisert et al. Appl. Phys. Lett. 83 (2003) 3930
SYOH 5.25 Do 18:00 B
Intermolecular Interactions in Thin Films of Subphthalocyanines
— •Christine Mattheus 1 , Wilfried Michaelis 1,2 , Dieter
Wöhrle 2 , and Derck Schlettwein 1 — 1 Physical Chemistry 1, University
of Oldenburg, Germany — 2 Institute of Organic and Macromolecular
Chemistry, University of Bremen, Germany
Thin films of SubphthalocyaninatoChloroBoron (SubPc) and its Fluorinated
Derivative (F12SubPc) have been prepared by physical vapour
deposition on NaCl, KBr, mica and glass. The intermolecular coupling
was studied in situ by UV- vis absorption spectroscopy and the structure
of the films was studied by X- ray diffraction (XRD). During deposition
of SubPc at 298 K optical spectra were obtained that were quite simi-
lar to spectra of the molecules in solution indicating negligible specific
intermolecular coupling in the films. After heating or during deposition
on heated substrates a spectral change was observed speaking for an
increased coupling in the films. The increased coupling of molecules in
annealed films led to an X- ray diffraction pattern of the films consistent
with the bulk crystal structure. The relative intensity in XRD shows
a preferential orientation of crystals with the ab-plane parallel to the
surface caused by an orientation of the molecules with their B-Cl axis
perpendicular to the surface and with their aromatic cone parallel to it.
As an additional parameter, the influence of fluorination on the growth
characteristics was also studied.
SYOH 5.26 Do 18:00 B
VUV-Spectroscopic Ellipsometry Investigations of DNA Base
Layers Deposited onto H-Si(111) Surfaces — •S. D. Silaghi 1 ,
Yu J. Suzuki 1 , O. D. Gordan 1 , C. Himcinschi 1 , G. Salvan 1 ,
M. Friedrich 1 , T. U. Kampen 1 , D. R. T. Zahn 1 , C. Cobet 2 , N.
Esser 2 , W. Richter 2 , and W. Braun 3 — 1 Institut für Physik, TU
Chemnitz, 09107 Chemnitz, Germany — 2 Institut für Festkörperphysik,
TU Berlin, 10623 Berlin, Germany — 3 BESSY GmbH, 12489 Berlin-
Adlerhof, Germany
DNA bases (adenine, guanine, thymine, cytosine) have electronic properties
comparable to wide-gap semiconductors thus being promising candidates
for hybrid organic/silicon electronics. Vacuum Ultraviolet Spectroscopic
Ellipsometry (VUV-SE) was applied for the in situ optical characterization
of DNA base layers grown by organic molecular beam deposition
onto H-Si(111) under ultra-high vacuum conditions. VUV-SE
measurements were performed with a rotating analyzer-type ellipsometer
using synchrotron radiation as a light source. The spectra were recorded
at an incidence angle of about 68 o in the energy range from 2.5 to 10
eV. Additionally the samples were investigated ex situ using a variable
angle spectroscopic ellipsometer in the energy range from 0.8 to 5 eV.
The dielectric functions of the DNA base layers were determined in the
whole energy range.
SYOH 5.27 Do 18:00 B
Spectroscopic ellipsometric characterization of organic films deposited
via Organic Vapor Phase Deposition — •C. Himcinschi 1 ,
N. Meyer 2 , S. Hartmann 3 , M. Friedrich 1 , G. Strauch 2 , W.
Kowalsky 3 , M. Heuken 2 , and D.R.T. Zahn 1 — 1 Halbleiterphysik,
Technische Universität Chemnitz, Reichenhainerstr. 70, D-09107 Chemnitz,
Germany — 2 AIXTRON AG, Kackertstr. 15-17, D-52072 Aachen,
Germany — 3 Institut für Hochfrequenztechnik, Technische Universität
Braunschweig, Schleinitzstr. 22, D-38106 Braunschweig, Germany
Thin films of Tris-(8-hydroxyquinoline)-aluminum(III) (Alq3) and
N,N ′ -[Di-(1-naphthyl)-N,N ′ -diphenyl]-(1,1 ′ -biphenyl )-4,4 ′ -diamine
(α-NPD) were deposited onto 8” Si substrate by Organic Vapor Phase
Deposition. The thickness analysis by Variable Angle Spectroscopic
Ellipsometry revealed very uniform films with minor edge effects that
originate from the distortion of the flow profile in the vicinity of the
wafer edges. However, even including these effects the standard deviation
for the thickness considering 21 points along one sample diameter is
below 1 nm in all cases.
The refractive indices and extinction coefficients of Alq3 and α-NPD
were determined from ellipsometry in the spectral range from 0.8 eV
up to 5 eV. These optical constants were derived using a multi-sample
analysis approach that employs simultaneous point-by-point fitting of ellipsometric
spectra recorded for samples with different thicknesses of the
organic layer.
SYOH 5.28 Do 18:00 B
Determination of the Anisotropic Optical Properties for Perfluorinated
Vanadyl Phthalocyanine Thin Films — •O. D. Gordan
1 , M. Friedrich 1 , W. Michaelis 2 , R. Kr öger 3 , T. Kampen 1 ,
D. Schlettwein 2 , and D. R. T. Zahn 1 — 1 Institute of Physics, University
of Technology Chemnitz, — 2 Physical Chemistry 1, Institute of
Pure and Applied Chemistry, — 3 Institute of Solid State Physics, University
of Bremen, D-28334
Thin films of perfluorinated vanadyl phthalocyanine F16PcVO were
prepared by physical vapor deposition (PVD) in high vacuum on fused silica
and KBr substrates. The absorption spectra in the visible region show
that the films on different substrates have different structure. The optical
constants for F16PcVO films were obtained in the spectral range of 0.7
- 4.5 eV from the simulation of ellipsometry spectra with an anisotropic
uniaxial model. From the difference between the in-plane and out-of-