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Kick-Off for the new funding period

SFB 1083 kick-started the new funding period with a workshop and public lecture

SFB 1083 kick-off workshop for its second funding period focussed on its new external projects based at the Peter-Grünberg-Institute, part of the Forschungszentrum Jülich, and the University of Münster.
Special highlight of the day was the widely announced invited lecture by Prof. Dr. Pedro M. Echenique from the Donostía International Physics Center in San Sebastián, Spain.

Dr. Alrun Hauke (Project A2) receives Dr. Walter-Seipp-Preis for her dissertation at TU Dresden

The SFB congratulates Dr. Alrun Hauke, a young postdoc in project A2 (Witte), for being awarded the annual Dr.-Walter-Seipp-Prize of Commerzbank Dresden in recognition of her outstanding PhD-dissertation on “Vertical Organic Field-Effect Transistors – On the Understanding of a Novel Device Concept” submitted at Technical University Dresden in 2016.

Initiated in the Nineties, Commerzbank Dresden each year honors the three highest-ranked theses submitted at the Technical University Dresden during the year before. On June 30, the Commerzbank in a small ceremony in its Event-Lounge in Dresden honored the three top-rated PhD-theses of 2016. The prize for the best dissertation, the Dr. Walter-Seipp-Preis and 4000 EUR, was awarded to Dr. Hauke.

Dr. Alrun Hauke’s thesis research was in the field of organic electronics under the guidance of Prof. Karl Leo (Inst. of Applied Physics) which led to a better understanding of a novel organic transistor, the so-called Vertical Organic Field-Effect Transistor (OFET). By combining experiments and data gained from device simulations she was able to identify the key parameters governing device operation as well as demonstrate improved devices with MOSFET-like inversion mode operation (MOSFET metal-oxide-semiconductor field-effect transistor=. The latter was facilitated by the concept of molecular doping, one of the primary research interests at the Institute of Applied Physics at TU Dresden.

We are pleased to have attracted Dr. Hauke to Marburg, where she joined project A2 in fall 2016. Within this project she now investigates interfaces between organic semiconductors and 2D materials with respect to their structural and electronic properties.

See also a press release in German issued by TU Dresden for more detail.

SFB 1083 “Internal Interfaces” extended by 4 years

Additional 10.5 Million Euros for Marburg’s Physicists and Chemists

Prof. Dr. Ulrich Höfer of the Department of Physics at Philipps-Universität Marburg is spokesman for the DFG’s Collaborative Research Center (SFB) 1083 “Structure and Dynamics of Internal Interfaces”. Photo: Philipps-Universität Marburg Rolf K. Wegst.

The German Research Foundation (Deutsche Forschungsgemeinschaft DFG) has granted Marburgs Collaborative Research Center (Sonderforschungsbereich) SFB 1083 „Structure and Dynamics of Internal Interfaces“ 10.5 Million Euros funding over the course of another four years until 2021. With this, the SFB – under guidance of its spokesman physicist Prof. Dr. Ulrich Höfer – will enter a new phase. The initial four years focussed on understanding the physical-chemical phenomena at interfaces, while the new focal point will be on controlling these phenomena and tailoring them for application.

Cooperation with partners in Jülich, Münster and Gießen

The new funding period will bring together 60 to 80 scientists in 18 research projects. One of these is located at the university in Münster (A13), one at the Peter-Grünberg-Institut in Jülich (A12), and two are located at the university in Gießen. Six projects are led by young research staff that has not yet attained a professorship.

New challenges: stacking of material layers and mixing of characteristics

In the new funding period SFB 1083 will also include research into novel two-dimensional materials. These single-atom-thick layers basically consist of “surface” only. In transfering newly gained insights into internal interfaces, SFB 1083’s researchers will build heterosystems with new effects by stacking layers of mixing characteristics of 2D-materials. By controlling these processes the scientists expect to offer the material sciences a modular assemblage box.  A new collaboration with a research center at Columbia University New York is part of this strategy.

See the full press release in German for detail.

Kenta Kuroda honored with “Academic Lecture Encouragement Prize”

Dr. Kuroda and Prof. Dr. Höfer in the lab at the University of Marburg (Photo: Univ. Marburg).

At the 36th academic lecture sponsored by the Japan Surface Science Association (SSSJ) held at the Nagoya International Conference Hall on November 29th in 2016, Kuroda gave an excellent general presentation on “Ultrafast dynamics of Dirac surface states in topological insulators” which is expected to make a significant contribution to the development of surface science.

Topological insulators are insulators in which only the outermost surface reveals a metallic state. As surface electrons are crucial in shaping the material functions, understanding details of the mechanics and processes at work has drawn worldwide attention. Kuroda and colleagues were the first to successfully apply short laser pulses and time-resolved photoelectron spectroscopy in the mid-infrared region in their investigations. As the researchers analyzed the photo excitation of Dirac surface-electrons generated in topological insulators at femtosecond resolution, they were able to show a direct optical transition of the Dirac surface condition in response to the mid-infrared excitation with a resulting spin-polarization of the surface current. The SSSJ sees this discovery as an important step to achieving optical spin control of electrons solely by the means of light.

The award is granted to promising young researchers under the age of 32 years and the presentation ceremony took place at the Surface Science Society of Japan’s regular meeting on May 20th, 2017.

The underlying research work was performed in close collaboration with colleagues in Japan and from SFB-project B6 (Höfer) during Dr. Kuroda’s research stay as a JSPS fellow and guest scientist of SFB 1083 at the Philipps-Universität Marburg in 2014 and 2015.

SFB 1083 Winter School at Schloss Rauischholzhausen

Castle Rauischholzhausen in winter (Photo: Castle Rauischholzhausen).

SFB 1083’s biannual winter school for its young researchers

More than 50 young staff-members involved in the various physics- and chemistry-based SFB 1083 subprojects have come together in Schloss Rauischholzhausen near Marburg for two days of talks and intensive discussion of their research. Invited speakers from Germany and abroad round of the program by contributing more technical tutorials and presentations of their research.

Invited Speakers: Ellen Backus (Mainz), Alexey Chernikov (Regensburg), Matteo Gatti (Gif-sur-Yvette), Christian Papp (Erlangen-Nürnberg), Katrin Siefermann(Leipzig)

Link to abstract-volume and report.

Interface between Silicon Technology and Organic Chemistry – Publication by A8 (Koert/Dürr) and B5 (Höfer)

Chemists and physicists of SFB projects A8 (Koert) and B5 (Höfer) demonstrate for the first time the controlled chemoselective attachment of bifunctional organic molecules to silicon.

Interface between semiconductor technology and organic chemistry: cyclooctyne selectively attaches to the Si-surface allowing additional functional groups to remain free (image: Marcel Reutzel & Michael Dürr; image may be used in reporting on the publication in JPCC only). Reprinted with permission from N. Reutzel et al, J. Phys. Chem. C 120, 46, 2016, 26284-26289. Copyright 2016 American Chemical Society.

With these results, which were highlighted on the cover page of The Journal of Physical Chemistry, an interface between silicon and organic multilayers has been created [1]. This interface opens the road for a controlled functionalization of silicon with organic molecules. In this way, it offers new perspectives in semiconductor technology (“More than Moore”).

Chemoselective attachment of multifunctional organic molecules is the first fundamental process step for the controlled organic functionalization of semiconductor surfaces. However, the high reactivity of pristine silicon surfaces, especially of the technologically most relevant Si(001) surface, has prohibited so far such a controlled functionalization: multifunctional molecules do not show chemical selectivity on these surfaces but are found with different functional groups attached.

In a joint effort, chemists and physicists of the SFB 1083 “Structure and Dynamics of Internal Interfaces” developed for the first time a general strategy for solving this problem: Using substituted cyclooctynes, they obtained well-defined inorganic-organic interfaces on Si(001) with the bifunctional molecules attached to the silicon surface solely via a cyclooctyne’s strained triple bond. The second functionality is thus available for further building up of complex molecular architectures, e.g., using organic click chemistry. The strategy for the observed chemoselectivity is based on the distinctly different adsorption dynamics of the separate functional groups and thus widely applicable.

In combination with the results for controlled multilayer synthesis in solution using the same classes of molecules [2], this work is a promising basis for a multitude of applications combining semiconductor technology and organic chemistry, e.g., the integration of optically active organic layers on silicon devices. The obtained structures are also of high interest for further studies of the electronic properties at organic/semiconductor interfaces within SFB 1083.

Publication:

[1] M. Reutzel, N. Münster, M. A. Lipponer, C. Länger, U. Höfer, U. Koert, M. Dürr, Chemoselective Reactivity of Bifunctional Cyclooctynes on Si(001),
J. Phys. Chem. C (2016), DOI: 10.1021/acs.jpcc.6b07501.

[2] N. Münster, P. Nikodemiak, and U. Koert, Chemoselective Layer-by-Layer Approach Utilizing Click Reactions with Ethynylcyclooctynes and Diazides,
Org. Lett. 18, 4296 (2016), DOI:10.1021/acs.orglett.6b02048.

See also press release in German.

Contact:
Prof. Dr. Ulrich Koert
Fachbereich Chemie, Philipps-Universität Marburg
Hans-Meerwein-Straße, D-35032 Marburg
Tel.: (+49) 6421 28-26970, Email: koert@chemie.uni-marburg.de

Prof. Dr. Michael Dürr
Institut für Angewandte Physik, Justus-Liebig-Universität Gießen
Heinrich-Buff-Ring 16, D-35392 Gießen
Tel: (+49) 641 9933-490, Email: michael.duerr@ap.physik.uni-giessen.de

Highly-ordered hybrids between organic semiconductors and MoS2 – Publication by A2 (Witte)

In a new publication in Physics Status Solidi Rapid Research Letters project A2 (Witte) reports on the fabrication of well-defined hybrids of organic semiconductors and transition metal-dichalcogenides (TMDCs).

The two-dimensional material graphene has garnered extreme interest due to its interesting electronic properties in combination with utmost structural stability despite merely nanometer thickness. Motivated by this prominent example, further two-dimensional materials have become the focus of today’s cutting-edge research. One important class of such materials are transition metal dichalcogenides such as MoS2, WS2 or MoSe2. Their interesting electronic properties have not only revealed novel physics but already enabled the fabrication of prototypical devices.

In their recent work, Tobias Breuer and Gregor Witte used such TMDC surfaces, in particular of MoS2, to fabricate crystalline, well-defined hybrid structures with organic semiconductors (OSCs), in themselve up-and-coming technologically relevant materials. Brought together, the characteristic advantages of both material classes can be combined to potentially fabricate novel synthetic materials with superior characteristics. The authors report on the successful fabrication of such hybrids combining MoS2 with the molecular donor and acceptor systems pentacene and perfluoropentacene. In particular, they observe that both materials are structurally compatible despite their strongly different shape symmetry and form
large crystalline islands on highly ordered MoS2 basal planes. Interestingly, the molecules arrange in such a fashion that the contact area at the interface between TMDC and organic semiconductor is maximized, hence allowing for an efficient coupling of both constituents. Surprisingly, the OSCs are even epitaxially aligned on the substrates.

A crucial aspect for the successful fabrication of these heterostructures is the structural quality of TMDC surfaces. In previous work, it has been shown that photoluminescence efficiency is strongly increased for MoS2 surfaces with significant defect density as compared to pristine surfaces. For the hybrid structures, the lateral dimensions of the crystalline OSC islands are reduced and the relative orientation of the molecules on the surface is inverted, hence leading to an upright molecular growth on defective MoS2 surfaces instead of a lying configuration on pristine
MoS2. Since the preparation of ideal, defect-free TMDC surfaces is challenging and commercially available TMDCs frequently have considerable defect densities, this aspect requires appropriate consideration. The achieved expertise on the preparation of such well-defined novel hybrid structures will enable the detailed investigation of their electronic and optical coupling mechanisms within further projects of SFB 1083.

Publication:

Tobias Breuer, Tobias Massmeyer, Alexander Mänz, Steffen Zoerb, Bernd Harbrecht, Gregor Witte
Structure of van der Waals bound Hybrids of Organic Semiconductors and Transition Metal Dichalcogenides: the Case of Acene Films on MoS2
Physica Status Solidi – Rapid Research Letters (2016).

Momentum space mapping of electron transfer processes in MoS2 – Publication by B6 (Höfer/Wallauer)

In a publication in Applied Physics Letters project B6 (Höfer) reports on a new experimental setup for time-resolved two-photon photoemission (2PPE). The method, which combines femtosecond pump-probe techniques with photoelectron spectroscopy, makes it possible to map the dynamics of electron transfer processes at surfaces and interfaces directly in momentum space.

The new experiment combines a high-harmonic generation (HHG) light source, developed and built in Marburg, with a state-of-the-art 3D hemispherical electron analyzer (VG Scienta DA30). The analyzer can measure electron energies as a function of both parallel momentum directions (kx and ky) without movement of the sample. The high-harmonic source gives access to the full 2D Brillouin zone whereas conventional 2PPE setups are restricted to electrons near the ? point.

The large parallel momenta, which become accessible with the new experiment, enable SFB 1083 to study electron dynamics at interfaces of many interesting new materials. Particularly, in the class of two-dimensional transition-metal dichalcogenides (TMDCs), most of the interesting electron dynamics take place at the boundary of the first Brillouin zone. Investigations of the intervalley scattering in the topmost layer of MoS2, a prototypical TMDC, demonstrate this capability. Electrons excited at the K-point are found to scatter to the Σ-point in less than 50 fs by directly mapping the electron population in k-space as a function of time.

The new experiment opens up the possibility to study charge transfer and exciton formation with 2PPE in a variety of systems, most prominently van-der-Waals heterostructures, which are a combination of different single-layer TMDCs. In these systems, upon excitation, charge transfer excitons can form. Their formation and relaxation pathways can now be examined by a direct mapping technique in momentum space.

Publication:

R. Wallauer, J. Reimann, N. Armbrust, J. Güdde, and U. Höfer
Intervalley scattering in MoS2 imaged by two-photon photoemission with a high-harmonic probe
Applied Physics Letters 109, 162102 (2016).

Prof. Echenique (GP1) receives Honorary Doctorate from Aalto University, Finland

We congratulate Prof. Dr. Pedro M. Echenique, PI of SFB-project GP1, on his honorary doctorate received from Aalto University, Finland.

In a ceremony on Oct.7th, Aalto University conferred an Honorary Doctorate in Technology on Pedro Miguel Echenique, Professor of the University of the Basque Country (UPV/EHU) and President of Donostia  international Physics Center (DIPC), together with another ten eminent persons in the fields of science, technology and society. The award, which is conferred every two years by Aalto University Schools of Technology, can look back on a tradition of more than 80 years, and among the recipients are renowned scientists, technologists and influencers in science and society with outstanding professional careers.
More details under Aalto University or DIPC-press release.

Dr. Tonner (A6) receives Hans G. A. Hellmann-Prize for Theoretical Chemistry

We congratulate Dr. Ralf Tonner, PI of SFB-project A6, on the prestigious prize awarded him by the working group on theoretical chemistry (AGTC) at the 52nd Symposium on Theoretical Chemistry held in Bochum.

Marburg chemist Dr. Ralf Tonner (right), PI of SFB 1083, receives the „Hans G. A. Hellmann-Preis für Theoretische Chemie“ from AGTC-president Prof. Dr. Christian Ochsenfeld. (Picture: Alexander Esser, Ruhr-Universität Bochum. Picture may be used in reporting on the award-process only.)

Dr. Tonner, who completed his habilitation in June, received the “Hans G. A. Hellmann-Prize for Theoretical Chemistry” in recognition of his ground-breaking contributions to a detailed theoretical understanding of the chemical processes at surfaces and interfaces. His research-project in SFB 1083 focuses on the detailed understanding of inorganic/organic interfaces from electronic structure theory.

Since 1999 the Hellmann-Prize has been awarded annually for outstanding scientific contributions in the field of theoretical chemistry. Recipients must be less than 41 years of age and not yet employed on a professorial position. However, all recipients to date succeeded in securing a permanent professorship within a couple of years after receiving the award.

German press release.

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