KIT IPS - News - Anomalous atomic vibrations in self-organized rare earth silicide nanoislands and nanowires unveiled

Anomalous atomic vibrations in self-organized rare earth silicide nanoislands and nanowires unveiled

Date: Dec 2025
The evolution of the atomic vibrations, described by the phonon density of states, from the bulk material to self-organized nanoislands and nanowires of the technology relevant rare earth silicide DySi2 is investigated. The results do not only clarify structural characteristics and unveil anomalies in important properties of this material, they also suggest strategies for their tailoring.

Phonons in epitaxial DySi2: from the bulk to self-organized nanoislands and nanowires

Thermal lattice excitations described by phonons, the quanta of lattice vibrations, govern basic material properties and important physical phenomena. In thin films and nanostructures, phonon dispersions and density of states, deviate drastically from the bulk counterparts due to a complex interplay of multiple factors. Achieving a comprehensive understanding of these deviations remains experimental and theoretical challenge.

Using in situ nuclear inelastic scattering, an advanced synchrotron radiation technique, scientists of the KIT in collaboration with the ESRF-The European Synchrotron in Grenoble, the Polish Academy of Sciences in Krakow, and the Wigner Research Centre for Physics in Budapest managed to experimentally determine the Dy-partial phonon density of states of bulk DySi₂ and self-organized nanoislands and nanowires on the Si(001) surface. The results reveal a softening of the crystal lattice of the nanoislands, which is further enhanced in the nanowires that significantly affects their thermodynamic and elastic properties. A comprehensive ab initio study unveils that the origin of these anomalies is the vibrations of the surface- and near-surface atoms as well as a very specific arrangement of Dy atoms on the Si(001) surface between the nanowires. Furthermore, the analysis demonstrate that, opposite to the widely accepted anisotropic lattice mismatch model, the nanowires grow with their length along the [0001] direction of the strained hexagonal unit cell.

The findings shed new light on the structural characteristics and vibrational dynamics of these technologically important nanostructures that may facilitate a precise predictive modeling of their properties and further advance their applications. Potentially, this may have important implications in fields like thermoelectric energy conversion, thermal management of micro- and nanoelectronics, spintronics, and quantum computing.

Original publication

S. Stankov, P. Piekarz, A. Seiler, D. G. Merkel, O. Bauder, R. Pradip, T. G. Baumbach, A. I. Chumakov, and R. Rüffer, Phonons in Epitaxial DySi₂: From the Bulk to Self-Organized Nanoislands and Nanowires Phys. Rev. Lett. 135, 256202 (2025), DOI: https://doi.org/10.1103/4r3t-tr77

(Left column) Dy-partial phonon density of states of DySi₂ bulk, nanoislands, and nanowires obtained at 115 K with the wave vector of the x-rays being parallel to the indicated directions of the Si(001) surface.

(Right column) Atomic force microscopy images of the DySi₂ bulk, nanoislands and nanowires samples.

Anomalous atomic vibrations in self-organized rare earth silicide nanoislands and nanowires unveiled

Original publication

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