Seminář ÚFKL: Margareta Wagner

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Margareta Wagner (CEITEC VUT Brno): In2O3(111): Surface Structure and Identification of OH Groups from Water Dissociation

Abstrakt:

Indium oxide, In2O3, is the prototypical transparent conductive oxide, and is omnipresent in any application where electronic and optical properties are of essence. Recently, also the chemical reactivity of In2O3 for selective hydrogenation of acetylene or CO2 was discovered. As the interface is central in all these applications, understanding the fundamental properties is critical, especially when going to nanoscopic dimensions in novel device architectures.

As a model system we investigate the non-polar In2O3(111) surface with low temperature Scanning Tunneling Microscopy and Atomic Force Microcopy (STM, AFM), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), and Density Functional Theory (DFT). The In2O3(111) unit cell features a total of 12 surface oxygen atoms in four inequivalent sites. A dissociated water molecule results in two hydroxyl groups adsorbed on the surface, but only one type of surface oxygen atoms is involved in the adsorption. With non-contact AFM we are able to identify not only the 12 individual topmost oxygen atoms of the In2O3(111) surface but also the individual OH groups formed upon water dissociation. Moreover, the hydrogen atom of the surface OH can be manipulated with the STM tip. This can lead to the formation of a new OH group by readsorbtion of the hydrogen atom on one of the inequivalently sited surface oxygen atoms nearby. In this work the individual OH groups are characterized and identified by their force-distance curves and thereby we are able to assess the proton affinity (i.e., the tendency to gain or lose a proton) of the surface oxygen atoms.