Specificity of electrophysical and gas-sensitive properties of nanocomposite ZnO-TiO2 films formed by solid-phase pyrolysis

Abstract

ZnO-TiO₂ thin films containing 0.5 mol%, 1.0 mol%, and 5.0 mol% ZnO were synthesized by oxidative solid-phase pyrolysis. The materials contained anatase and rutile phases with particle size of 6-13 nm, as confirmed using X-ray phase analysis and scanning electron microscopy. When a certain number of ZnO crystallites appeared in the TiO₂ film structure in the temperature range of room temperature to 220 °C, a two-level response of the film resistance was observed, differing by approximately 10%, as obtained by electrophysical measurements. The two-level response correlates with the formation of two donor energy levels of 0.28 and 0.33 eV in the band structure of the ZnO-TiO₂ films. The donor level with a higher activation energy corresponded to the Ti vacancy (V⁻_Ti), and that with a lower activation energy corresponded to the Zn vacancy (V⁻_Zn). Two levels of gas-sensitive properties were noted for 0.5ZnO-TiO₂, 1ZnO-TiO₂, and 5ZnO-TiO₂ under the influence of 50 ppm NO₂ at 250 °C. Such two-level responses can be ascribed to the pinning of the Fermi level on ZnO and TiO₂ nanocrystallites. The mechanism of the beak-shaped and two-level responses of sensors based on composite nanomaterials when exposed to various gases was elucidated.

Keywords

Thin film / ZnO / TiO₂ / Nanocomposites / Pyrolysis / Gas sensors

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Victor V. Petrov: Writing - review & editing, Writing - original draft, Validation, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization. Maria G. Volkova: Writing - original draft, Investigation, Formal analysis. Alexsandra P. Ivanishcheva: Visualization, Investigation, Data curation. Gleb V. Tolstyak: Investigation. Ekaterina M. Bayan: Writing - review & editing, Writing - original draft, Validation, Methodology, Data curation.

Acknowledgements

This research was financially supported by the Russian Science Foundation 24-29-00203 (https://rscf.ru/project/24-29-00203/) at the Southern Federal University. We express our gratitude to Professor V. V. Sysoev for discussing the research.

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