Humboldt Fellow Alexander Gray comes to HZB
Alexander Gray (here in his lab at Temple University, Philadelphia, USA) will strengthen his collaboration with the team of Florian Kronast at BESSY II. © Privat
Alexander Gray from Temple University in Philadelphia, USA, is working with HZB physicist Florian Kronast to investigate novel 2D quantum materials at BESSY II. With the fellowship from the Alexander von Humboldt Foundation, he can now deepen this cooperation. At BESSY II, he wants to further develop depth-resolved X-ray microscopic and spectroscopic methods in order to investigate 2D quantum materials and devices for new information technologies even more thoroughly.
Topological insulators and Weyl semimetals are among the most exciting classes of materials for quantum devices. They are characterised by the fact that they have different electronic and magnetic properties at the surfaces and interfaces than in the volume.
Alexander Gray is a well-known expert in this field and frequently comes to BESSY II for short measurement periods, where he cooperates with Florian Kronast. As a Fellow of the Alexander von Humboldt Foundation, the American physicist can now finance regular guest stays at HZB with Florian Kronast's team and at Forschungszentrum Jülich with Claus Schneider's team. "The Humboldt Fellowship gives us more time, so we can investigate and discuss in more detail how the interplay between surface, interface and bulk properties in quantum materials leads to novel phenomena that enable device applications," he says.
Gray leads a team at Temple University in Philadelphia and also plans to send his students to BESSY II. "We want to develop new techniques to study the electronic and magnetic properties of 2D quantum materials and quantum devices in more detail," he outlines his goals. At BESSY II, Gray will primarily develop depth-resolved standing-wave photoemission microscopy further for this purpose. Kronast, Gray, and his former doctoral advisor Chuck Fadley have already combined this method with excitation by standing X-ray waves to enable depth resolution (SW-PEEM).
From mid-August, Alexander Gray is planning his first stay at BESSY II. He is not only looking forward to the measurements and many discussions, but also to the typical Berlin atmosphere: "The people are really open and friendly, and I have never experienced the famous "Berlin snout". I think if I do one day, I might deserve it." With this attitude, full of humor, his stay in Berlin will be a huge success in every aspect.
- A simpler way to inorganic perovskite solar cellsInorganic perovskite solar cells made of CsPbI3 are stable over the long term and achieve good efficiencies. A team led by Prof. Antonio Abate has now analysed surfaces and interfaces of CsPbI3 films, produced under different conditions, at BESSY II. The results show that annealing in ambient air does not have an adverse effect on the optoelectronic properties of the semiconductor film, but actually results in fewer defects. This could further simplify the mass production of inorganic perovskite solar cells.
- Spintronics: A new path to room temperature swirling spin texturesA team at HZB has investigated a new, simple method at BESSY II that can be used to create stable radial magnetic vortices in magnetic thin films.
- BESSY II: How pulsed charging enhances the service time of batteriesAn improved charging protocol might help lithium-ion batteries to last much longer. Charging with a high-frequency pulsed current reduces ageing effects, an international team demonstrated. The study was led by Philipp Adelhelm (HZB and Humboldt University) in collaboration with teams from the Technical University of Berlin and Aalborg University in Denmark. Experiments at the X-ray source BESSY II were particularly revealing.