Temperature and Ambient Band Structure Changes in SnO2 for the Optimization of Hydrogen Response

Petros-Panagis Filippatos, Anastasia Soultati, Nikolaos Kelaidis, Dimitris Davazoglou, Maria Vasilopoulou, Charalampos Drivas, Stella Kennou, Alexander Chroneos

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Abstract

Tin dioxide (SnO2) is one of the most used materials for sensing applications operating at high temperatures. Commonly, “undoped SnO2” is made by precursors containing elements that can have a deleterious impact on the operation of SnO2 sensors. Here, we employ experimental and theoretical methods to investigate the structural properties and electronic structure of the rutile bulk and surface SnO2, focusing on unintentional doping due to precursors. Unintentional doping from precursors as well as intrinsic doping can play an important role not only on the performance of gas sensors, but also on the properties of SnO2 as a whole. The theoretical calculations were performed using density functional theory (DFT) with hybrid functionals. With DFT we examine the changes in the electronic properties of SnO2 due to intrinsic and unintentional defects and we then discuss how these changes affect the response of a SnO2-based gas sensor. From an experimental point of view, we synthesized low-cost SnO2 thin films via sol–gel and spin-coating processes. To further enhance the performance of SnO2, we coated the surface with a small amount of platinum (Pt). The crystalline structure of the films was analyzed using x-ray diffraction (XRD) and scanning electron microscopy (SEM), while for the determination of the elements contained in the sample, X-ray photoelectron spectroscopy (XPS) measurements were performed. Furthermore, we investigated the effect of temperature on the band structure of SnO2 in air, in a vacuum and in nitrogen and hydrogen chemical environments. To optimize the response, we used current–voltage characterization in varying environments. The aim is to associate the response of SnO2 to various environments with the changes in the band structure of the material in order to gain a better understanding of the response mechanism of metal oxides in different pressure and temperature environments. We found that the resistance of the semiconductor decreases with temperature, while it increases with increasing pressure. Furthermore, the activation energy is highly affected by the environment to which the thin film is exposed, which means that the thin film could respond with lower energy when exposed to an environment different from the air.
Original languageEnglish
Article number96
Number of pages14
JournalInorganics
Volume11
Issue number3
Early online date27 Feb 2023
DOIs
Publication statusPublished - Mar 2023

Bibliographical note

Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/)

Funder

P.-P.F.: A.C. and N.K. are grateful for funding from the Lloyd’s Register Foundation, a charitable foundation helping to protect life and property by supporting engineering-related education, public engagement, and the application of research. Publisher Copyright: © 2023 by the authors.

Keywords

  • tin dioxide
  • sensors
  • DFT
  • experiments

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