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.

cosmicdustparticle

Micrometeorite. X-ray microtomography section of partially molten porous cosmic dust particle (approximately 170 micrometers in size).


High-lights of the year 2014 included results of a study on random diffusion of atomic vacancies in graphene and replaying evolutionary transitions from the dental fossil record.
Imperfections in the regular atomic arrangements in crystals determine many of the properties of the material, and their diffusion is behind many microstructural changes in solids. However, imaging non-repeating atomic arrangements is extremely difficult in conventional materials. In a recent study, we have for the first time directly imaged diffusion of an atomic defect in graphene, the recently discovered two-dimensional carbon nanomaterial, over long image sequences. The key advance in this study was the usage of a state-of-the art microscope combining ultra-high vacuum and low acceleration voltage to reduce the effects of residual gas particles and electron-beam-induced sputtering of carbon atoms. This study opens a new route for the direct study of defect migration and diffusion in low dimensional materials, which can also lead to new insights into. This study was partially funded through a three-year project by University of Helsinki Funds, and was carried out in collaboration with the group of Jannik Meyer at the University of Vienna, Austria. The images were recorded by Jani Kotakoski with a recently installed Nion UltraSTEM 100 microscope in Vienna. The study was published in Nature Communications in 2014 (Kotakoski et al., Nat. Commun. 5, doi:10.1038/ncomms4991)

The relationships of extinct species in the course of evolution are primarily determined by the morphological characteristics in fossils, such as the shape and size of teeth and bones. The interpretation of evolutionary links may be substantially affected by similarities and
differences in these morphological characters, but understanding of these similarities in the frame-work of developmental biology is challenging. The development of morphological features, such as the shape of the face or the shape of a tooth surface, are determined in a growing embryo by signalling molecules that communicate information between differentiating cells. The signalling molecules ultimately derive from the DNA, the changes of which are the mechanism of evolution. In this research, it was shown that by manipulating the signalling molecules in growing extant animal teeth it is possible to generate organ morphologies of extinct organisms. Morphology of teeth whose signalling molecules were tinkered /in vivo/ were studied utilizing high-resolution x-ray microtomography. This novel linkage of developmental understanding of growth and the morphological tools used in paleontological studies of fossil materials provides potential for new insight in the appearance and linkage of various characteristics in the fossil record (Harjunmaa et al., Nature, 512,  doi:10.1038/nature13613)

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