When electrically charged particles are shot at thin layers of material with great speed, several physical effects can be triggered. These effects can play an important role in very different areas of research - from materials science to cancer therapy. Anna Niggas investigated such effects as part of her dissertation at the Institute of Applied Physics at TU Wien. She received her doctorate with the highest distinction ‘Sub Auspiciis Preasidentis’ and is now also awarded the Hannspeter Winter Prize of TU Wien on 24 January 2025.

High speed and high charge

Electrically charged particles can be accelerated relatively easily and can be made to impinge on a sample at any desired speed - all that is required is a suitable electric field. The stronger the field, the greater the kinetic energy of the particle and the more powerful the impact on the material surface. “However, the ions we use for our experiments differ not only in their kinetic energy, but also in their charge state,” explains Anna Niggas. “And that can make a huge difference.”

If an electron is taken away from an electrically neutral atom, it becomes a positively charged ion. A larger atom such as xenon - with 54 protons and 54 electrons - can also be stripped of several electrons. It is then referred to as a ‘highly charged ion’.

When such a highly charged ion strikes a material surface or penetrates a thin layer of material, it not only transfers its kinetic energy to the impact region, it also snatches electrons from the material due to its high electrical charge.

Electrons flying away

Such an impact is therefore a complicated process in which a large number of particles are involved. It can also happen that electrons are hurled away - and this is exactly what Anna Niggas has now investigated in her dissertation. “Both the number and the energy of these electrons can be measured, using different ions and different materials”, says Anna Niggas. This makes it possible to find out exactly which processes play a role and why different materials react differently to ion bombardment.

For example, small holes appear in certain materials when they are bombarded with highly charged ions - this can be utilised to specifically produce a porous membrane. Other materials, on the other hand, are surprisingly unharmed after being penetrated by ions.

These findings play a role in many areas of research - in order to specifically change material surfaces, to characterise the properties of different materials, and even for nuclear fusion such effects are important: in a nuclear fusion reactor, charged particles constantly hit the material of the reactor wall, and the reactor should suffer as little damage as possible. The interaction of ions and various materials is even important for space technology: the solar wind also consists of charged particles that can cause damage to spacecraft.

Anna Niggas

Anna Niggas grew up in Vienna and studied physics at TU Wien. After spending time abroad in Uppsala (Sweden), she conducted research in the group of Prof Richard Wilhelm at the Institute of Applied Physics. She has already presented her results in a whole series of publications in prestigious journals and at numerous international conferences, and completed her dissertation ‘Sub Auspiciis Praesidentis’ in 2023. A whole series of awards now underline her success, such as the Sheldon Datz Prize at the international ICPEAC conference in 2023, last Tuesday she received the Loschmidt Prize from the Austrian Chemical-Physical Society for her dissertation and now also the Hannspeter Winter Prize from TU Wien.

Hannspeter Winter Prize for outstanding dissertation

Since 2008, the Hannspeter Winter Prize has been awarded annually to a female graduate of TU Wien's doctoral programme. The research prize, endowed with 10,000 euros, is jointly financed by TU Wien and the BA/CA Foundation and honours the legacy of TU Professor Hannspeter Winter, who was highly committed to promoting young female scientists. As a former member of the Institute of Applied Physics and a pioneer in the research of highly charged ions, Hannspeter Winter was closely associated with Anna Niggas' field of research. In the 17 years of its existence, the prize is now returning to the Institute of Applied Physics for the second time through the honouring of Anna Niggas.

Contact

Dr. Anna Niggas
Institut für Angewandte Physik
Technische Universität Wien
+43 1 58801 13433
anna.niggas@tuwien.ac.at