Dr. László Óvári

Extreme Light Infrastructure ALPS, Szeged, Hungary
László Óvári received his PhD in 2000 at the University of Szeged, Hungary. He was postdoc and senior researcher at the Reaction Kinetics and Surface Chemistry Research Group in Szeged, interrupted by several research visits at the Free University Berlin in 2006-2007 and the University of Erlangen in 2012 and 2013. His research focusses on (photo) electron and ion spectroscopy of metal, oxide, and carbide single crystalline surfaces, model catalysts, 2D materials and photoinduced processes. Since 2015 he is a group leader at the Extreme Light Infrastructure ALPS in Hungary, where he is responsible for the NanoESCA end station.

Talk title: Hexagonal boron nitride monolayers on metals and alloys: relevance for templating and model catalysis 
Surface templating is a highly promising route towards designing large-scale artificial atomic and molecular nanostructures with tailored chemical, quantum or spin functionalities. From the manifold of procedures, surface templating by electrostatic potentials is the least invasive way to steer the growth of adsorbates on surfaces. As an example, the templating ability of a periodically undulating hexagonal boron nitride (h-BN) monolayer on Rh(111) stems from the local surface potential difference between the closer pore and farther wire regions. Recently we demonstrated that it is possible to enhance the local work function nanopatterning by using Au/Rh(111) surface alloys as a substrate. Beside the electronic tuning, structural parameters of h-BN can also be controlled by the amount of gold. While corrugated h-BN monolayers are known templates for molecules and clusters adsorbed on top of them, we extend this functionality towards the subsurface. Moreover, by changing the chemical nature of the substrate metal, we can also influence other properties of h-BN: with an interfacing gold layer between h-BN and Rh(111), the thermal stability of boron nitride can be significantly improved. Metal clusters supported by h-BN are increasingly used as non-oxidic model catalysts. Thereby it is important to reveal thermally induced processes of the model catalyst itself. The observed behavior differs significantly for admetals of different reactivity. While for gold nanoparticles sintering, intercalation and desorption are the dominant phenomena on h-BN/Rh(111), the more reactive Rh nanoparticles are able to disrupt the BN bonds as well, allowing the diffusion of BN fragments on top of Rh clusters. Examples for model catalytic studies related to the transformation of ethanol and acetaldehyde will also be presented. The applied methods span core level and angle resolved valence band photoemission (momentum microscopy), other electron and ion spectroscopic methods, STM and DFT calculations.