Photoemission Fingerprints for Structural Identification of Titanium Dioxide Surfaces

TL;DR

This study demonstrates that photoemission spectroscopy can reliably identify and analyze the surface structures and orientations of TiO₂ polymorphs, including mixed nanosized powders, by using Ti LMV Auger templates.

Contribution

It introduces a method using Ti LMV Auger templates for quantitative surface structural identification of TiO₂ polymorphs and orientations.

Findings

Ti LMV decay reflects Ti 4sp-O 2p hybridizations.

Templates enable analysis of mixed nanosized powders.

Method agrees with X-ray diffraction results.

Abstract

The wealth of properties of titanium dioxide relies on its various polymorphs and on their mixtures coupled with a sensitivity to crystallographic orientations. It is therefore pivotal to set out methods that allow surface structural identification. We demonstrate herein the ability of photoemission spectroscopy to provide Ti LMV (V = valence) Auger templates to quantitatively analyze TiO$_2$ polymorphs. The Ti LMV decay reflects Ti 4sp-O 2p hybridizations that are intrinsic properties of TiO$_2$ phases and orientations. Ti LMV templates collected on rutile (110), anatase (101), and (100) single crystals allow for the quantitative analysis of mixed nanosized powders, which bridges the gap between surfaces of reference and complex materials. As a test bed, the anatase/rutile P25 is studied both as received and during the anatase-to-rutile transformation upon annealing. The agreement with X-ray diffraction measurements proves the reliability of the Auger analysis and highlights its ability to detect surface orientations.