Fakultät für Physik
> Zum Inhalt
2019-01-10 [ ]

Polarons catch editor's eye

Together with colleagues at the University of Vienna, Michele Reticcioli and Cesare Franchini, the Surface Physics group of the Institute of Applied Physics has found that polarons can localise on CO molecules adsorbed on TiO2(110). The editors of Physical Review Letters have selected this work as 'editor's choice'.

A Polaron moves to the surface of Titaniumdioxide after a CO molecole is adsorbed on it

Polaron formation plays a major role in determining the structural, electrical, and chemical properties of ionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, and atomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reduced rutile TiO2(110) surface. Adsorbed CO shows attractive coupling with polarons in the surface layer, and repulsive interaction with polarons in the subsurface layer.

As a result, CO adsorption depends on the reduction state of the sample. For slightly reduced surfaces, many adsorption configurations with comparable adsorption energies exist and polarons reside in the subsurface layer. At strongly reduced surfaces, two adsorption configurations dominate: either inside an oxygen vacancy, or at surface Ti5c sites, coupled with a surface polaron. Similar conclusions are predicted for TiO2(110) surfaces containing near-surface Ti interstitials.

These results show that polarons are of primary importance for understanding the performance of polar semiconductors and transition metal oxides in catalysis and energy-related applications.