A single defect in the atomic structure alters the properties of materials

The positions of atoms tell us about electrical conductivity, among other things. By studying related defects, new technologies are discovered for, for example, the utilisation and transmission of electricity.

What are your research topics?

I study atomic-level point defects in gallium nitride and other materials.

All properties of all materials are dictated by the identity of the atoms that constitute them, and by the order and spatial position of these atoms. As the number of atoms in even a small piece of material is colossal, of the order of 1,000,000,000,000,000,000,000 (1021, that is 1 followed by 21 zeros), the identity and location of each atom cannot be determined individually.

Instead, a number of methods are needed to determine the general features of the atomic-level structure with a sufficient degree of precision.

My method of choice is shooting antimatter (positrons) at pieces of matter and studying positron-electron annihilation radiation, which reveals details of ‘missing atoms’, or structures where an atom is missing contrary to expectations. These are known as vacancy defects.

Where and how does the topic of your research have an impact?

The vacancy defects mentioned above determine the most important properties of, among others, semiconductors at very dilute concentrations. A single atom missing from among a trillion, or an atom located in the wrong place, dramatically changes electrical conductivity and optical properties, which are of the utmost importance to, for example, nitride semiconductors that are the basis of solid-state LED lighting and Blu-ray technology.

Detailed understanding of the properties of point defects helps in developing new components. Knowing the associated effects makes it possible to develop, for instance, energy-efficient technologies for the future.

What is particularly inspiring in your field right now?

I’m inspired by the development of new approaches to the generation and storage of antimatter. In a few decades, these technologies could be utilised, for example, in spacecraft propulsion.

Filip Tuomisto is the professor of experimental materials physics at the Faculty of Science.

Watch Filip Tuomisto's inaugural lecture as a new professor on the 8th of September on YouTube.

Read about the other newly appointed professors here.