Materials physics

The division carries out research in the following fields: ion beam interactions with matter, ion beam analysis, nanostructures, electronic structures, microtomography, computational materials physics, electronics, medical physics and solid earth geophysics.

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Swift heavy ion impact in silicon dioxide. Bright colors indicate hot electrons in the vicinity of the impact area.


The way how an ion interacts with a material greatly depends on its velocity. The fundamentals of ion-solid interactions are well understood for low velocities, when the ion travels through the material without inducing electronic excitations.  The situation is much more complicated at higher velocities (so called swift heavy ions) where electronic excitations become non-negligible. Dense electronic excitations are produced in a cylindrical region of only about ten nanometers in diameter but up to tens of microns in length. In electrical insulators, this results in a structural transformation in the material with similar dimensions, known as a swift heavy ion track. The formation mechanisms of swift heavy ion tracks have been a subject of a debate over half a century.

This kind of nanoscale precision in the excitation is unique to swift heavy ions and they therefore have great potential of becoming a future tool to modify materials at the nanoscale. It has been already demonstrated that swift heavy ions can be used the change the shape of nanoparticles buried several microns deep in the material. Ion tracks are already used, for example, to produce industrial filters and printed circuit boards. In geology, tracks are used to determine the age of rocks and to study their thermal history.

While in principle computer simulations could reveal the mysteries behind ion track formation, in practice, the computations are too heavy for the current computing technology.  However, the simulations can be made faster with suitable approximations. We implemented and further developed a computer simulation method that can describe electronic excitations orders of magnitude faster than the conventional methods by assuming that the electronic subsystem of the material becomes thermalized after the impact. The predictions from the model were consistent with experimental studies, suggesting the model can be used in the future to understand track formation.

Leino A. A., Daraszewicz S. L., Pakarinen O. H., Nordlund K. and Djurabekova F., 2015, Atomistic two-temperature modelling of ion track formation in silicon dioxide. Europhysics Letters 110,16004

Ion beam analysis laboratory and laboratory for nanomaterials

Laboratory of electronic structure and laboratory of microtomography

Computational materials science

Medical physics

Electronics

Solid earth geophysics