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SFB 1083 Winter School at Schloss Rauischholzhausen

17. January 2017/in News /by sfb1083

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)

25. November 2016/in News /by sfb1083

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.

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

8. November 2016/in News /by sfb1083

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).

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