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Plenarvorträge - DPG-Tagungen

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Symposium Organic and Hybrid Systems for Future Electronics Donnerstag<br />

Bragg and diffuse scattering allows us to identify screw- and edge dislocations<br />

as the main defects on the molecular scale. We quantify dislocation<br />

densities obtained for different substrate preparations and discuss their<br />

potential relation to transport properties.<br />

SYOH 5.16 Do 18:00 B<br />

Morphology of Pentacene and Tetraazapentacene grown on<br />

SiO2 and vacuum deposited Polytetrafluoroethylene substrates.<br />

— •Paul Quinn 1 , S Schrader 1 , L Brehmer 1 , G Jarosz 1 , V<br />

Failla 1 , and K Gritsenko 2 — 1 Condensed Matter Physics, Institute<br />

of Physics, University of Potsdam, Germany — 2 Institute of Semiconductor<br />

Physics NASU, Kiev, Ukraine<br />

The growth and morphology of the pentacene based thin films, grown<br />

under ultra high vacuum, on SiO2 and vacuum deposited polytetrafluoroethylene<br />

was studied using AFM/STM, ellipsometry and polarisation<br />

dependent second harmonic generation. The films were grown under a<br />

wide range of experimental conditions with variations in the depositions<br />

rates, substrate temperatures, and geometries employed to optimise the<br />

structural ordering. Polytetrafluoroethylene, of particular interest due to<br />

the demand for low-k dielectric materials in semiconductor devices, is<br />

shown to form highly ordered films. It was found that the ordering of<br />

the pentacene and tetraazapentacene is greatly increased on the polytetrafluoroethylene<br />

surface. The ordering of the polytetrafluoroethylene<br />

and the ability of this film to promote ordering of the pentacene films<br />

is discussed. Acknowledgement: The work was supported by Marie-Curie<br />

Host Fellowships: Project MODERN No.HPMD-CT-2001-00083 and by<br />

the RTN EUROFET HPRN-CT-2002-00327<br />

SYOH 5.17 Do 18:00 B<br />

Substrate and temperature dependent lateral order in N,N’dibutyl-substituted<br />

quinacridone monolayer studied by MBD-<br />

LEED — •Feng Lin, Dingyong Zhong, Lifeng Chi, and Harald<br />

Fuchs — Physikalisches Institut, Universität Münster, D-48149<br />

Münster, Germany<br />

Ordered monolayers of N,N’-dibutyl-substituted quinacridone (QA4C)<br />

were prepared by vacuum sublimation on Cu(110),Ag(110), and Ag(111)<br />

surfaces. Using Low energy electron diffraction that was designed specially<br />

to follow the growth processes and thus obtain the kinetics of<br />

growth phenomena, the nucleation, grwoth, and superstructures of QA4C<br />

monolayers were investigated and compared. The strong interlayer interaction<br />

between the QA4C molecules and Cu(110) surface results in very<br />

low surface diffusivity at room temperature. Consequently, the commensurate<br />

monolayer structure of QA4C was only obtained when annealing<br />

the substrate up to 420 K and its crstallographic parameters were determined<br />

by the substrate lattice rather than the bulk structure of QA4C<br />

itself. While for Ag(110) surface, the QA4C monolayer tended to arrange<br />

the molecules in accordance with its bulk crystallography. The<br />

microscopic mechanism might be the intralayer interaction of H-bond<br />

between molecules which becomes significant since the interlayer interaction<br />

is weaker than the case of Cu(110). Temperature induced structural<br />

transition was observed on Ag(111), where the six symmetry-equivalent<br />

domains at room temperature was changed to a single domain that was<br />

more similar to its bulk crystallography at about 200 K.<br />

SYOH 5.18 Do 18:00 B<br />

Structure and growth morphology of CuPc thin films — •S.<br />

Kowarik 1 , A. Gerlach 1 , N. Kishimoto 1,2 , R. Jacobs 1 , and F.<br />

Schreiber 1 — 1 Physical and Theoretical Chemistry Laboratory, Oxford<br />

University, South Parks Road, Oxford OX1 3QZ, UK — 2 Department<br />

of Chemistry, Tohoku University, Aoba-ku, Sendai 980-8578, JAPAN<br />

We present a study of the growth and structure of thin films of the<br />

organic semiconductor copper-phthalocyanine (CuPc) on SiO2. Films up<br />

to a thickness of 2000 ˚A have been studied as a function of the growth<br />

parameters (temperature and growth rate) by x-ray diffraction, spectroscopic<br />

ellipsometry and atomic force microscopy. The films exhibit a<br />

change in morphology from smooth films to needle-shaped crystallites<br />

depending on growth temperature. This transition is associated with a<br />

change from low crystallinity in smooth films to high crystallinity in<br />

rough films. Measurements of the geometric film parameters (thickness<br />

and roughness) with spectroscopic ellipsometry and x-ray diffraction allow<br />

for a comparison of the two techniques. The results are compared to<br />

measurements on thin films of the fluorinated version F16CuPc (1, 2).<br />

1. J. O. Osso et al., Advanced Functional Materials 12, 455-460 (2002).<br />

2. M. I. Alonso et al., Journal of Chemical Physics 119, 6335-6340<br />

(2003).<br />

SYOH 5.19 Do 18:00 B<br />

Structural and Morphological Properties of N,N´-DiMethyl-<br />

3,4,9,10-PeryleneTetraCarboxylic DiImide Films on Passivated<br />

GaAs(100) Substrates — •G. Salvan, S. Silaghi, G. Baumann,<br />

T.U. Kampen, R. Scholz, and D.R.T. Zahn — Institut für Physik,<br />

Technische Universität Chemnitz, 09107 Chemnitz, Germany<br />

Amongst the many-fold applications of organic thin films the use as active<br />

interlayers in metal/inorganic semiconductor junctions for the highfrequency<br />

and microwave technology is very promising. A route to achieve<br />

better device performance is to control the morphology of the organic film<br />

by changing the substrate temperature for the film growth. Raman spectroscopy<br />

was employed to investigate in situ the structural properties<br />

and the morphology of N,N´-DiMethyl-3,4,9,10-PeryleneTetraCarboxylic<br />

DiImide films deposited onto S-passivated GaAs(100) substrates in ultrahigh<br />

vacuum at various temperatures. Complementary scanning electron<br />

microscopy studies revealed that all the films consist of islands. The crystalline<br />

nature of these islands was proven by the observation of libronic<br />

phonon-like modes of the molecular crystal in the Raman spectra. The<br />

decrease in the phonon band widths observed at elevated substrate temperatures<br />

is related to an increase in the size of the crystalline domains<br />

and improvement of crystallinity.<br />

SYOH 5.20 Do 18:00 B<br />

Structural investigation of the low temperature order-disorder<br />

phase transition of NTCDA on Ag(111) using NIXSW — •C.<br />

Stadler, J. Stanzel, M. Scheuermann, S. Hansen, C. Kumpf<br />

und E. Umbach — Exp. Physik II, Uni Würzburg<br />

The properties of organic thin films largely depend on their interaction<br />

with the underlying substrate. For NTCDA on Ag(111) the bonding is<br />

regarded as chemisorption as revealed e. g., by photoemission or thermal<br />

desorption spectroscopy. Recently an unusual phase transition upon<br />

cooling of NTCDA (sub)monolayers on Ag(111) has been observed by<br />

electron diffraction studies and other techniques. Upon cooling the long<br />

range order disappears below 180 K. Normal Incident X-Ray Standing<br />

Waves (NIXSW) measurements were performed using the wiggler beamline<br />

ID32 at the ESRF. We report on detailed structural results of different<br />

room temperature and low temperature phases, especially on the precise<br />

bonding distance between the NTCDA molecules and the Ag substrate.<br />

A comparison of the NIXSW results obtained from photoemissionand<br />

Auger-yield measurements enables a reasonable correction for nondipolar<br />

contributions to the photoeletron yield as well as for electron<br />

induced Auger processes. Both effects cannot be neglected for small atomic<br />

species.<br />

SYOH 5.21 Do 18:00 B<br />

Doping and Diffusion Properties of Na in PTCDA Thin Films<br />

— •Jens Wüsten, Steffen Berger, Stefan Lach, and Christiane<br />

Ziegler — University of Kaiserslautern, Department of Physics,<br />

Erwin-Schrödinger-Straße 56, D-67663 Kaiserslautern<br />

In order to investigate the electronic and vibronic properties of n-doped<br />

PTCDA (perylene-3,4,9,10-tetracarboxylic-dianhydride), thin films were<br />

grown under UHV conditions. The n-doping was performed by subsequently<br />

evaporating sodium (Na) from a dispenser source, followed by<br />

one or several annealing steps to reach a homogeneous distribution of<br />

the dopant throughout the layer.<br />

Experimental results from electronic (XPS/UPS/IPE), conductivity,<br />

Seebeck, vibration (FT-IR), angle resolved XPS and SIMS measurements<br />

of Na doped PTCDA before and after annealing will be presented. The<br />

changes in the elctronic structure and the electrical properties show that<br />

doping is already established after Na evaporation. However, the results<br />

suggest that the model of an initially built doped surface layer and a<br />

subsequent diffusion of Na into the PTCDA bulk during the annealing<br />

step is incorrect. In fact evidences could be found, that the deposited<br />

dopant initially establishes a homogeneous distribution in the PTCDA<br />

layer and is partially removed during the annealing step.<br />

SYOH 5.22 Do 18:00 B<br />

Radiotracer diffusion measurements of noble metal atoms<br />

in crystalline organic films — •Michael Scharnberg 1 , Jörn<br />

Kanzow 1 , Rainer Adelung 1 , Klaus Rätzke 1 , Franz Faupel 1 ,<br />

Christoph Pannemann 2 , Ulrich Hilleringmann 2 , and Jens<br />

Pflaum 3 — 1 Technische Fakultät, CAU Kiel, Kaiserstr. 2, 24143 Kiel<br />

— 2 Department EIM-E/Sensorik, Univ. Paderborn — 3 3. Physikalisches<br />

Institut, Univ. Stuttgart<br />

The application of organic field effect transistors (OFETs) for large

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