NUKFER

Novel sample environments and X-ray optics for in situ resonant nuclear scattering studies of geological, biological and nanotechnological iron-based materials

The aim of the NUKFER project is to obtain a comprehensive understanding of the changes in the phonon density of states of materials with orders of magnitude in the nanometer and subnanometer range and thus to gain control over the lattice dynamics on the nanometer scale. In order to achieve this goal, in-situ inelastic nuclear magnetic resonance scattering experiments with nano-focused X-rays are carried out on individual nano-objects on the Dynamics Beamline P01 at PETRA III. A compact ultra-high vacuum chamber, equipped with a nanoscanner and X-ray transparent beryllium windows has been specifically designed for the project. Combined with suitable Kirkpatrick-Baez-Optics this enables the investigation of individual nano-objects. 

Fig. 1: the UHV chamber for in situ nuclear magnetic resonance scattering experiments on individual nano-objects. (A) UHV chamber with control units for pressure measurement, ion pump and bakeout unit, (B) rear side of the UHV chamber with Be window for diffracted outgoing X-rays, (C) front view with Be window for incident X-rays, (D) UHV chamber in a tailor-made heating jacket and (E) specially made sample holder mounted on the nanopositioning unit.

A systematic investigation of the change in the Fe-partial phonon density and the resulting thermoelastic properties is carried out on the model of individual, self-organized, metallic and semiconducting FeSi2 nanowires, nano-islands and nanoclusters with different sizes, shapes and crystal phases. Ab initio calculations carried out by a cooperation partner provide complementary understanding of the electronic properties and experimental results.

 

Fig. 2, upper-left: AFM images of the sample surface. lower-left: ab initio calculations of the element- and direction-specific PDOS for α-FeSi2. right: Measured PDOS of the nanostructures (black symbols), result of the modeling (red line with the respective polarization components (green and gray-dashed area).

The reduction of the layer thickness to a few atomic layers allows us to observe drastic changes in the phonon density of states as well as the thermodynamic and elastic properties of the layers in the immediate vicinity of the interface.

Using the instrumentation developed as part of the NUKFER project, nuclear magnetic resonance scattering experiments on individual nano-objects will be carried out on the nuclear magnetic resonance beamline ID18 at the modernized European Synchrotron ESRF-EBS, where synchrotron radiation with a nanofocused beam will be available for user experiments.

The project is funded by the BMBF (05K16VK4).

Publication

Lattice dynamics of β−FeSi2 nanorods (-> link)
J. Kalt, M. Sternik, I. Sergueev, M. Mikolasek, D. Bessas, J. Göttlicher, B. Krause, T. Vitova, R. Steininger, O. Sikora, P.T. Jochym, O. Leupold, H.-C. Wille, A.I. Chumakov, P. Piekarz, K. Parlinski, T. Baumbach and S. Stankov
Phys. Rev. B 106, 205411 (2022)

 

Lattice dynamics and polarization-dependent phonon damping in α-FeSi2 nanostructures (-> link)
J. Kalt, M. Sternik, B. Krause, I. Sergueev, M. Mikolasek, D. Bessas, O. Sikora, T. Vitova, J. Göttlicher, R. Steininger, P. T. Jochym, A. Ptok, O. Leupold, H.-C. Wille, A. I. Chumakov, P. Piekarz, K. Parlinski, T. Baumbach and S. Stankov
Phys. Rev. B 101, 165406 (2020)

 

Lattice dynamics of endotaxial silicide nanowires (-> link)
J. Kalt, M. Sternik, B. Krause, I. Sergueev, M. Mikolasek, D.G. Merkel, D. Bessas, O. Sikora, T. Vitova, J. Göttlicher, R. Steininger, P.T. Jochym, A. Ptok, O. Leupold, H.-C. Wille, A.I. Chumakov, P. Piekarz, K. Parlinski, T. Baumbach and S. Stankov
Phys. Rev. B 102, 195414 (2020)

 

Ab initio and nuclear inelastic scattering studies of Fe3Si/GaAs heterostructures (-> link)
O. Sikora, J. Kalt, M. Sternik, A. Ptok, P. T. Jochym, J. Łażewski, P. Piekarz, K. Parlinski, I. Sergueev, H.-C. Wille, J. Herfort, B. Jenichen, T. Baumbach, and S. Stankov
Phys. Rev. B 99, 134303 (2019)

 

Lattice dynamics of epitaxial strain-free interfaces (-> link )

J. Kalt, M. Sternik, I. Sergueev, J. Herfort, B. Jenichen, H.-C. Wille, O. Sikora, P. Piekarz, K. Parlinski, T. Baumbach and S. Stankov Phys. Rev. B Rapid Communications 98, 121409(R) (2018)

 

See also EurekAlert! press release (-> link )