Discovery of crystal phase transition may enable controlled structure transformation

A Finnish-Japanese joint research project has produced first-rate results by discovering a phase transition in the structure of crystalline materials in atomistic simulations. The research is part of the joint project “Novel approach to Fabrication of Microsystems within Joint Finnish-Japanese Collaboration” funded by the Academy of Finland.

In the research, fine, atomic-scale needles were pushed onto crystal surfaces. The sudden movement of the needle has traditionally been understood in terms of the movement of dislocations in the crystal structure. The results achieved in the project, however, suggest that it may in semiconductors be a question of a crystalline-to-crystalline phase transition. The discovery may in the future enable controlled structure transformation.

The results of the molecular dynamic simulations by Dr Dariusz Chrobak and Professor Roman Nowak from the Nordic Hysitron Laboratory of Helsinki University of Technology, together with Professor Kai Nordlund from the Helsinki University Accelerator Laboratory were published in Physical Review Letters on 26 January 2007.

The Nordic Hysitron Laboratory (NHL) international research group is part of the Department of Materials Science and Engineering at Helsinki University of Technology. The main target of NHL is mechanical characterisation of advanced materials and nanostructures using a Hysitron TriboIndenter capable of high precision probing (depth resolution 0.2 nm) of solid surfaces. The experiments are coupled with finite element and atomistic simulation of the explored nanometer-size contacts performed in cooperation with Professor Nordlund and his team from the Accelerator Laboratory at the University of Helsinki.