Atomic structure and crystallographic shear planes in epitaxial TiO2 anatase thin films

Abstract

We report on the high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmissionelectron microscopy (HAADF-STEM) study of TiO2 anatase thin films grown by pulsed laser deposition on LaAlO3 substrates.The analysis provides evidence of a peculiar growth mode of anatase on LaAlO3 that is characterized by the formation ofan epitaxial layer at the film/substrate interface. In particular, the film is split into two adjacent slabs of about 20 nm each, bothdisplaying the same Bravais lattice compatible with the anatase tetragonal cell. The formation of two different families of crystallographicshear (CS) superstructures is observed within the film, namely (103)- and (101)-oriented CS plane structures, occurringin the outer film region and in proximity of the film/substrate interface, respectively. HAADF analysis and Energy DispersiveSpectroscopy highlight the occurrence of Al interdiffusion from the substrate into the film region. By combining HRTEM results,image simulation techniques and DFT calculations we determine the atomic structure of the CS planes, and show that they arecubic-TiO-based structures analogous to the TinO2n-1 Magnéli phases derived from rutile.


Autore Pugliese

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  • Ciancio R.; Vittadini A.; Selloni A.; Aruta C.; Scotti di Uccio U.; Rossi G.; Carlino E.

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Anno di pubblicazione

2012

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