Benedikt Roesner.jpg

Dr. Benedikt Rösner

PostDoc X-ray Optics Group

Paul Scherrer Institut
Laboratory for Micro- and Nanotechnology
ODRA / 106
5232 Villigen PSI

Telephone: +41 56 310 2454

Highlights and Research

Extreme ultraviolet vortices at free electron lasers

Extreme ultraviolet vortices can be described as radiation which carries an orbital angular momentum. In electromagnetic radiation from free electron laser and synchrotron sources, the electric and magnetic field can rotate uniformly clockwise or counterclockwise with respect to the light propagation, resulting in circular polarization. In vortices, it is the phase of the electromagnetic field that rotates around a circularity in a helical fashion. The vortex can be characterized with an integer-numbered topologic charge, which describes how often the wavefront is shifted around 360°.
To demonstrate optical vortices at free electron lasers, we fabricated spiral zone plates, which yield a diffraction pattern with such a phase singularity. The material of choice for the extremely intense EUV radiation of the FERMI free electron laser is silicon. We thus etched spiral zone plates into ultraflat thin silicon membranes, and characterized the radiation using a Hartmann wavefront sensor in the far field.
Viewpoint in APS Physics :: Wavefront Characterization of Optical Vortices - Phys. Rev. X

Beam profiling of free electron laser radiation in the focus of a Fresnel zone plate is a true challenge. An established method to characterize extremely intense beams in the EUV and soft X-ray regime is to shoot imprint craters into a material with well known damage attenuation length and threshold, and to characterize the form of the imprint crater. However, this method is limited to a dynamical range of approx. 100, with the consequence that the X-ray fluence has to be varied to get the full beam profile from maximum intensity to faint beam tails. We now adapted a method known from grayscale lithography of PMMA and treated imprint craters with organic solvents (or developers). In this way, additional material, which is exposed to radiation but not ablated, can be removed. We are able to show that the adapted method is extremely sensitive and enhances the dynamic range for beam profiling by an order of magnitude to 1000.
Beam Profiling by Development of Polymer Imprints - Opt. Express

X-ray microscopy beyond 10 nm

9 nm ZP.jpg A 9 nm zone plate - diameter: 240 µm, outermost zone width: 8.8 nm, energy correction: 750 eV

Fresnel zone plates are diffractive lenses widely used in X-ray microscopy. As an intrinsic limit from diffraction, their resolution is approximately in the order of their outermost zone width. This induces a major challenge in nanofabrication to produce smaller and smaller nanostructures striving for better resolution. In recent years, zone dimensions and resolution in X-ray micrscopy have been approaching the 10 nanometre level.
We now aimed for demonstrating resolution beyond 10 nm. While zone plates have been reported on with focal spots well below 10 nm (cp. Mohacsi et al., Sci. Rep. 2017, Döring et al., Opt. Express 2013) reconstructed from the farfield, directly recorded X-ray micrographs have not been obtained so far. We thus fabricated zone plates with iridium zones with 9 nm (see above), and tested their resolution at the Hermes beamline at Soleil and the Pollux beamline at the Swiss Light Source. Indeed, these zone plates prove to be capable of resolving test structures with typical sizes below 10 nm. The following image shows a well-resolved periodic iridium structure with 9 nm line width.
A publication is in preparation. 9 nm XRM.jpg Micrograph of a test structure consisting of periodic iridium lines with 9 nm line width and averaged transmission along the x-direction of the scan.

Single shot, time-resolved demagnetization dynamics at free electron lasers

Time Streaking.jpg Magnetization dynamics of a CoDy film measured in transmission with circularly polarized light in a single shot. The experiment was performed in May 2016 at FERMI. The time window covered with the off-axis zone plate is approx. 1.5 ps, the duration of the IR pump laser is in the order of 100 fs.

X-ray free electron lasers exhibit unique capabilities to conduct resonant x-ray spectroscopy techniques on ultrafast time scales. Utilizing diffractive optical elements, the pathway difference inherent to diffraction can be exploited to streak the arrival time of an x-ray probe along a geometric dimension. This concept has been applied in a pioneering experiment in reflection geometry at FLASH with a time resolution of 120 fs: Single-shot Monitoring of Ultrafast Processes via X-ray Streaking at a Free Electron Laser.
Adapting the experiment to a transmission geometry, we investigated demagnetization dynamics of a CoDy film together with collaborators from CNRS, the University Pierre and Marie Curie, and at the FERMI free electron laser, see figure above. The time window reachable with this setup is 1.5 ps, theoratically limited by the wavelenght divided through the speed of light. In practice, the duration of the pump puls of approx. 100 fs is the limiting factor. &BR& Extending this scheme to take advantage of the other spatial dimension, more advanced experiments become possible, such as single-shot, time-resolved spectroscopy (see figure below).
A publication is in preparation.

Sub-10 nm guiding patterns for block co-polymer self-assembly

Approaching the fundamental limits of electron beam lithography, novel methods are required for large-scale fabrication of extremly small feature sizes. Bottom-up approaches such as self-assembly of block co-polymers offer promising perspectives in nanofabrication. However, the self-assembly has to be guided to prevent random assembly. For this purpose, we fabricated a topological guiding pattern for block co-polymers consisting of approx. 30-40 nm high silicon oxide lines with line widths below around or even below 10 nm. These guiding patterns are then utilized by our collaborators at the Institute of Microelectronics of Barcelona IMB-CNM for self-assemlby of PS-PMMA block co-polymers. Details are about to follow. A publication is in preparation.

Sub-10 nm electron beam lithography using line-doubling

5 nm test pattern.jpg A test pattern for resolution tests - 5 nm iridium-doubled lines on an HSQ template, height of approx. 70 nm

Pushing the limits of electron beam lithography, we aim for the fabrication of nanostructures in the regime below 10 nm. Using the established method of line-doubling by fabricating a sparse template and subsequent coating with metal films in an atomic layer deposition system, we are able to fabricate structures with line widths down to 5-6 nm. The structures can be utilized in diffractive optical elements (see above), or test structures for determining microscopy resolution.

Nanoscience Foundries and Fine Analysis

nffa-logo.png The European NFFA project sets out a platform to carry out comprehensive projects in nanotechnology research, in particular granting access for scientists to methods in nanofabrication. As scientific backbone of the project, we address bottlenecks in nanoscience research with our partners all over Europe.


Benedikt Rösner
Dr. rer. nat.
Scientific Research
Jan 2016 - up to now PostDoc in the X-ray Optics and Applications group at the Paul Scherrer Institut
Academic background
Oct 2011 - Dec 2015 Dissertation at the Friedrich-Alexander-Universität Erlangen-Nürnberg in Physical Chemistry
"Microspectroscopic Insights into the Electronic Switching of Organic and Metal-Organic Nanostructures"
Oct 2006 - Sep 2011 Bachelor and Master studies in chemistry at the FAU Erlangen-Nürnberg
Jul 2010 - Jan 2011 Research semester at the University of Wollongong, Australia
Community service and school education
May 2006 - Sep 2006 Employment as ambulance officer
Aug 2005 - Apr 2006 Community service as ambulance assistant
Sep 1996 - Jul 2005 Gymnasium with focus on natural sciences
Scientific societies and programs
Mar 2013 HERCULES School at the ESRF and ILL facilities in Grenoble
Feb 2013 TEM School at the Center for Nanoanalysis and Electron Microscopy
  Deutsche Physikalische Gesellschaft (DPG)



B. Rösner, F. Döring, P. R. Ribič, D. Gauthier, E. Principi, C. Masciovecchio, M. Zangrando, J. Vila-Comamala, G. de Ninno, C. David
High Resolution Beam Profiling of X-ray Free Electron Laser Radiation by Polymer Imprint Development
Optics Express, 25, 2017, 30686-30695

P. R. Ribič, B. Rösner, D. Gauthier, E. Allaria, F. Döring, L. Foglia, L. Gianessi, N. Mahne, M. Manfredda, C. Masciovecchio, R. Mincigrucci, N. Mirian, E. Principi, E. Roussel, A. Simoncig, S. Spampinati, C. David, G. de Ninno
Extreme-Ultraviolet Vortices from a Free-Electron Laser
Physical Review X, 7, 2017, 031036

F. Marschall , Z. Yin , M. Beye , J. Buck , F. Döring , V. A. Guzenko , K. Kubicek , J. Rehanek , D. Raiser , B. Rösner , A. Rothkirch , S. T. Veedu , J. Viefhaus , C. David, S. Techert
Transmission zone plates as analyzers for efficient parallel 2D RIXS-mapping
Scientific Reports, 7, 2017, 8849

F. Marschall, D. McNally, V. A. Guzenko, B. Rösner, M. Dantz, X. Lu, L. Nue, V. Strocov, T. Schmitt, C. David
Zone plates as imaging analyzers for resonant inelastic x-ray scattering
Optics Express, 25, 2017, 15624

I. Mohacsi, I. Vartiainen, B. Rösner, M. Guizar-Sicairos, V. A. Guzenko, I. McNulty, R. Winarski, M. V. Holt, C. David
Interlaced zone plate optics for hard X-ray imaging in the 10 nm range
Scientific Reports, 7, 2017, 43624


B. Rösner, U. Schmidt, R. H. Fink
In-operando studies of Ag-TCNQ nanocrystals using Raman and soft x-ray microspectroscopy
XRM Conference Proceedings, 849, 2017, 012016

K. Ran, B. Rösner, B. Butz, R. H. Fink, E. Spiecker
Switching behaviour of individual Ag-TCNQ nanowires: An in situ transmission electron microscopy study
Nanotechnology 27, 2016, 425703


B. Rösner, M. Milek, A. Witt, B. Gobaut, P. Torelli, R. H. Fink, M. M. Khusniyarov
Reversible Photoswitching of a Spin-Crossover Molecular Complex in the Solid State at Room Temperature
Angewandte Chemie Int. Ed. 54, 2015, 12976-12980

B. Rösner, K. Ran, B. Butz, U. Schmidt, E. Spiecker, R. H. Fink
A microspectroscopic insight into the resistivity switching of individual Ag-TCNQ nanocrystals
Physical Chemistry Chemical Physics 17, 2015, 18278-18281

N. Zeilmann, B. Rösner, A. Späth, U. Schmidt, R. H. Fink
Nanomorphology in thin films of acetamide end-functionalised quaterthiophene
Thin Solid Films 583, 2015, 108-114


B. Rösner, D. M. Guldi, J. Chen, A. I. Minett, R. H. Fink
Dispersion and Characterization of Arc Discharge Singe-Walled Carbon Nanotubes - Towards Conducting Transparent Films
Nanoscale 6, 2014, 3695-3703

B. Rösner, N. Zeilmann, U. Schmidt, R. H. Fink
Employing microspectroscopy to track charge trapping in operating pentacene OFETs
Organic Electronics 15, 2014, 435-440


B. Rösner, A. Späth, R. H. Fink
The role of solvation effects in the growth of TCNQ-based charge-transfer salts
Journal of Crystal Growth 380, 2013, 34-38

J. Forster, B. Rösner, R. H. Fink, L. C. Nye, I. Ivanovic-Burmazovic, K. Kastner, J. Tucher, C. Streb
Oxidation-driven self-assembly gives access to high-nuclearity molecular copper vanadium oxide clusters
Chemical Science 4, 2013, 418-424


J. Forster, B. Rösner, M. M. Khusniyarov, C. Streb
Tuning the light absorption of vanadium clusters
Chemical Communications 47, 2011, 3114-3116