Noncontact atomic force microscopy (nc-AFM) has recently proven to be a powerful tool for characterizing surfaces of complex materials.1 In this talk I will first discuss the capabilities of achieving atomic resolution and chemical identification of surface atoms, using a challenging system of copper oxide thin films. Copper oxides play a key role in catalysis of small organic molecules, and they form a plethora of structures with a-priori unknown configurations and stoichiometry. Here the system is resolved by a combination of nc-AFM and theoretical methods based on a combination of density functional theory and machine learning.

The second part of the talk will focus on possibilities of investigating electrons self-trapped in the crystal lattice, so called polarons.2 Such charge carriers can move to adjacent lattice positions, provided they are given certain activation energy. Polarons play a key role in many applications and materials properties, such as electrical conductivity, optical properties, catalysis and photocatalysis, and they stand behind exotic properties such as colossal magnetoresistance or high-temperature superconductivity. The successful imaging of polarons in hematite Fe₂O₃ and SrTiO₃ will be shown, and the new possibilities offered by this technique will be discussed.

References:

[1] Giessibl, F. J. The qPlus sensor, a powerful core for the atomic force microscope. Rev. Sci. Instr. 90, 011101 (2019).

[2] Franchini, C., Reticcioli, M., Setvin, M. & Diebold, U. Polarons in Materials. Nature Reviews Materials 6, 560-586 (2021).

*corresponding author: e-mail: martin.setvin@matfyz.cuni.cz