XPS and DFT study of Sn incorporation into ZnO and TiO2 host matrices by pulsed ion implantation

TL;DR

This study combines experimental XPS analysis and DFT calculations to investigate how tin incorporates into ZnO and TiO2 matrices via pulsed ion implantation, revealing substitutional doping and clustering behaviors.

Contribution

It provides a comprehensive analysis of Sn incorporation mechanisms in ZnO and TiO2, highlighting differences in defect formation and clustering tendencies.

Findings

Sn substitutes for Zn2+ and Ti4+ in ZnO and TiO2, respectively

Interstitial occupation and Sn clustering observed in TiO2 films

DFT calculations explain the prevalence of substitutional defects

Abstract

Bulk and thin films ZnO and TiO2 samples were doped with Sn by pulsed ion implantation and studied by means of X-ray photoelectron core-level and valence band spectroscopy as well as density functional theory calculations for comprehensive study of the incorporation of Sn. XPS spectral analysis showed that isovalent Sn cation substitution occurs in both zinc oxide (Sn2+ -> Zn2+) and titanium dioxide (Sn4+ -> Ti4+) for bulk and film morphologies. For TiO2 films, the implantation also led to occupation of interstitials by doped ions, which induced the clustering of substituted and embedded Sn atoms; this did not occur in ZnO:Sn film samples. Density functional theory (DFT) formation energies were calculated of various incorporation processes, explaining the prevalence of substitutional defects in both matrices. Possible mechanisms and reasons for the observed trends in Sn incorporation into the ZnO and TiO2 matrices are discussed.