Nc-AFM on complex oxides

Martin Setvin

Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic

TU Wien, Vienna, Austria

Abstract

I will discuss our recent results on oxide surfaces achieved by nc-AFM. In the first part of the seminar, the possibility of using nc-AFM for investigation of electron- and hole-polarons will be demonstrated. The method will be illustrated on two nearly-insulating materials: Doped hematite Fe₂O₃ and the KTa_1-xNb_xO₃ perovskite. Charge carriers can be injected into the material and create a cloud of charged particles trapped in the lattice. The cloud expands due to electrostatic interactions and thermally activated polaron hopping. Controlled annealing of this cloud and its characterization by KPFM provides valuable information on polaron dynamics that is compared to KMC simulations.   

The second part of the seminar will be focused on bulk-terminated perovskites KTaO₃ and SrTiO₃, their preparation by in-situ cleaving and the role of (incipient) ferroelectricity on the cleaving process. The (incipient) ferroelectric properties offer interesting options in catalysis due to the enhanced freedom of relaxation of the transition metal ions. The influence of this effect on the adsorption of molecules will be demonstrated on an example of CO adsorption, where the molecule strongly couples to the ferroelectric lattice relaxations and to excess electrons in the material. 

Support from GACR 20-21727X and GAUK Primus/20/SCI/009 is acknowledged.