SFB 1083 in partnership with Chemikum Marburg supports Girls’ Day 2019

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SFB 1083’s Ö-project closely cooperates with Chemikum Marburg e.V. by installing at its premises several new experiments and workshops providing hands-on insights into the SFB’s research objective and the study methods employed. In 2019, for a second time, the partnership supported Girls’ Day activities with dedicated offerings.

Girls’ Day 2019 with its 50 young (agegroup 10-16) female participants benefitted from these offerings, which included the application of acid-base-reactions, measuring thermal signatures of chemical reactions and electrical conductivity in various substances. The experiments provide insight into the central research aspect of SFB 1083: “What are the reactions taking place at the interface, that is the contact between two materials?”

“Girls’ Day allows us to showcase how researchers work. In interesting experiments and workshops we can entice enthusiasm for MINT-disciplines in female pupils”, state Prof. Stefanie Dehnen and Dr. Christof Wegscheid-Gerlach, director and co-director of Chemikum Marburg and principal investigators of SFB 1083’s Ö-project.

A special informatics-focused workshop, in cooperation with Michael Szabo (Fachdidaktik Informatik PUM/MLS), showcased how disciplines work together and how modern research needs detailed programming for optimal analytical results. The SFB’s Atomic Force Microscope (AFM), for example, needs a complex range of operational programming to realize its full potential. This was demonstrated using the Lego-model and it rapidly became obvious to the riveted audience how programming controls the instrument’s operation. 18 girls were then guided in developing their own little programs using the language scratch. At the end of the 3-hour workshop the young participants had all succeeded in letting their “dog run around the lake” and teasing out the impact of minor changes to their code.

See also a press release in German.

Contact

Dr. Christof Wegscheid-Gerlach
Chemikum Marburg
SFB 1083 project Ö
Tel.: 06421 28 25252
EMAIL

Organic monolayers can reduce contact resistances in organic electronics – Publication by A2 (Witte)

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In a detailed study, Felix Widdascheck, Alrun Hauke and Gregor Witte from SFB-project A2 show how phthalocyanine monolayers can be used to control the work function of noble metal electrodes, both in single crystalline model systems and for real life polycrystalline electrodes.

The work function of bare metal surfaces (yellow) can be modified by a thin layer of phthalocyanines (blue) to reduce injection barriers in organic electronic devices. (Image: F. Widdascheck).

Work function tailoring by means of organic monolayers is one of several promising approaches to reducing the contact resistance at the interface between metal electrodes and organic semiconductors in organic electronics devices.

In their study Felix Widdascheck and coauthors used several polar and non-polar phthalocyanines to modify the work functions of noble metal electrodes. As a starting point, they performed a detailed STM and Kelvin probe analysis of the coverage-dependent work function changes of Au and Ag single crystal surfaces. The authors find that the work function changes strongly depend on both coverage and the type of phthalocyanine used as the contact primer. Their phenomenological description of the observed trends provides important groundwork for more detailed theoretical modeling of the processes taking place at the complex internal interface between metal, monolayer and organic semiconductor.

In a further step towards actual device applications, the authors then transferred their findings and the developed preparation protocols to polycrystalline electrodes, demonstrating that the same work function changes can be observed also on “real-life” electrodes. With the end user in mind, the team also tested the air stability of their contact primers, proving that a sacrificial phthalocyanine multilayer serves well to protect the highly ordered mono- and bilayer contact primers during air transfer and can be removed by thermal desorption afterwards.

Publication

F. Widdascheck, A.A. Hauke and G. Witte,
A Solvent-Free Solution: Vacuum-Deposited Organic Monolayers Modify Work Functions of Noble Metal Electrodes
Adv. Funct. Mater. (2019) DOI: 10.1002/adfm.201808385

See also press release in German.

Contact

Prof. Dr. Gregor Witte
Philipps-Universität Marburg
SFB 1083 project A2
Tel.: 06421 28 21384
EMAIL

New ways of controlling and analyzing organic reactions on silicon surfaces – Publications by A8 (Koert/Dürr) & B5 (Höfer/Mette) and A6 (Tonner)

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In a joint effort, the groups of SFB-projects A8 and B5 used scanning tunneling microscopy for controlling the final products of a textbook-type reaction of organic molecules on silicon surfaces. A detailed understanding of the driving forces of these reactions are obtained by means of energy decomposition analysis as developed in SFB-project A6.

The isomers naphthalene (left) and azulene (right) bind very differently to a copper surface: While naphthalene forms a weak bond (physisorption), azulene engages in a strong chemical bond with substantial charge transfer (chemisorption).

Ether cleavage on silicon is the surface analogue of an SN2 reaction; SN2 reactions represent the textbook example for how to control solution-based chemical reactions by means of steric hinderance or the choice of solvent. In an STM study published in Angewandte Chemie, the team around Gerson Mette and Michael Dürr has now shown that tip-induced ether cleavage on Si(001) leads to additional final products which are not obtained by thermal activation. Moreover, different final products can be selectively addressed by different excitation channels, either direct excitation by electron transfer or multiple excitation of vibrational modes. As the two channels can be selectively addressed by the tunneling bias, a new way of reaction control was achieved.

In parallel, the advances in the theoretical description of these systems are illustrated in a review article by Lisa Pecher and Ralf Tonner. Within the framework of density functional theory, the chemists of A8 successfully applied energy decomposition analysis to extended systems in order to derive bonding concepts for molecules on surfaces. This allows to interpret experimental results and predict new reaction schemes.

Publications

G. Mette, A. Adamkiewicz, M. Reutzel, U. Koert, M. Dürr, and U. Höfer,
Controlling an SN2 reaction by electronic and vibrational excitation ‐ tip‐induced ether cleavage on Si(001)
Angew. Chemie Int. Ed. 58/11 (2019) 3417-3420 DOI: 10.1002/anie.201806777
L. Pecher and R. Tonner,
Deriving bonding concepts for molecules, surfaces, and solids with energy decomposition analysis for extended systems
WIREs Comput. Mol. Sci. (2018) (21pp) DOI:10.1002/wcms.1401

See also joint press release by the universities of Gießen and Marburg under the auspices of the Forschungscampus Mittelhessen ( in German).

Contact

Prof. Dr. Michael Dürr
Justus-Liebig-Universität Gießen
SFB 1083 project A8
Tel.: 0641 993490
EMAIL