SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>

SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>

Thin-film n-n nanoheterostructures of SnO<sub>2</sub>/TiO<sub>2</sub>, highly sensitive to NO<sub>2</sub>, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO<sub>2</sub&...

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Main Authors: Piotr Nowak, Wojciech Maziarz, Artur Rydosz, Kazimierz Kowalski, Magdalena Ziąbka, Katarzyna Zakrzewska
Format: Article
Language:English
Published: MDPI AG 2020-11-01
Series:Sensors
Subjects:
gas sensors
SnO2
TiO2
thin films
Langmuir-Blodgett technique
Online Access:https://www.mdpi.com/1424-8220/20/23/6830
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spelling doaj-96fec45c29bc47a68c5cd34fef6ed8692020-11-30T00:01:41ZengMDPI AGSensors1424-82202020-11-01206830683010.3390/s20236830SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>Piotr Nowak0Wojciech Maziarz1Artur Rydosz2Kazimierz Kowalski3Magdalena Ziąbka4Katarzyna Zakrzewska5Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandFaculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandFaculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandFaculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandFaculty of Materials Science and Ceramics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandFaculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, PolandThin-film n-n nanoheterostructures of SnO<sub>2</sub>/TiO<sub>2</sub>, highly sensitive to NO<sub>2</sub>, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO<sub>2</sub> base layers were deposited by MS and subsequently overcoated with a thin and discontinuous TiO<sub>2</sub> film by means of L–B. Rutile nanopowder spread over the ethanol/chloroform/water formed a suspension, which was used as a source in L–B method. The morphology, crystallographic and electronic properties of the prepared sensors were studied by scanning electron microscopy, SEM, x-ray diffraction, XRD in glancing incidence geometry, GID, x-ray photoemission spectroscopy, XPS, and uv-vis-nir spectrophotometry, respectively. It was found that amorphous SnO<sub>2</sub> films responded to relatively low concentrations of NO<sub>2</sub> of about 200 ppb. A change of more than two orders of magnitude in the electrical resistivity upon exposure to NO<sub>2</sub> was further enhanced in SnO<sub>2</sub>/TiO<sub>2</sub> n-n nanoheterostructures. The best sensor responses R<sub>NO2</sub>/R<sub>0</sub> were obtained at the lowest operating temperatures of about 120 °C, which is typical for nanomaterials. Response (recovery) times to 400 ppb NO<sub>2</sub> were determined as a function of the operating temperature and indicated a significant decrease from 62 (42) s at 123 <b>°</b>C to 12 (19) s at 385 <b>°</b>C A much smaller sensitivity to H<sub>2</sub> was observed, which might be advantageous for selective detection of nitrogen oxides. The influence of humidity on the NO<sub>2</sub> response was demonstrated to be significantly below 150 <b>°</b>C and systematically decreased upon increase in the operating temperature up to 400 <b>°</b>C.https://www.mdpi.com/1424-8220/20/23/6830gas sensorsSnO2TiO2thin filmsLangmuir-Blodgett technique
collection DOAJ
language English
format Article
sources DOAJ
author Piotr Nowak
Wojciech Maziarz
Artur Rydosz
Kazimierz Kowalski
Magdalena Ziąbka
Katarzyna Zakrzewska
spellingShingle Piotr Nowak
Wojciech Maziarz
Artur Rydosz
Kazimierz Kowalski
Magdalena Ziąbka
Katarzyna Zakrzewska
SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
Sensors
gas sensors
SnO2
TiO2
thin films
Langmuir-Blodgett technique
author_facet Piotr Nowak
Wojciech Maziarz
Artur Rydosz
Kazimierz Kowalski
Magdalena Ziąbka
Katarzyna Zakrzewska
author_sort Piotr Nowak
title SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
title_short SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
title_full SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
title_fullStr SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
title_full_unstemmed SnO<sub>2</sub>/TiO<sub>2</sub> Thin Film n-n Heterostructures of Improved Sensitivity to NO<sub>2</sub>
title_sort sno<sub>2</sub>/tio<sub>2</sub> thin film n-n heterostructures of improved sensitivity to no<sub>2</sub>
publisher MDPI AG
series Sensors
issn 1424-8220
publishDate 2020-11-01
description Thin-film n-n nanoheterostructures of SnO<sub>2</sub>/TiO<sub>2</sub>, highly sensitive to NO<sub>2</sub>, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO<sub>2</sub> base layers were deposited by MS and subsequently overcoated with a thin and discontinuous TiO<sub>2</sub> film by means of L–B. Rutile nanopowder spread over the ethanol/chloroform/water formed a suspension, which was used as a source in L–B method. The morphology, crystallographic and electronic properties of the prepared sensors were studied by scanning electron microscopy, SEM, x-ray diffraction, XRD in glancing incidence geometry, GID, x-ray photoemission spectroscopy, XPS, and uv-vis-nir spectrophotometry, respectively. It was found that amorphous SnO<sub>2</sub> films responded to relatively low concentrations of NO<sub>2</sub> of about 200 ppb. A change of more than two orders of magnitude in the electrical resistivity upon exposure to NO<sub>2</sub> was further enhanced in SnO<sub>2</sub>/TiO<sub>2</sub> n-n nanoheterostructures. The best sensor responses R<sub>NO2</sub>/R<sub>0</sub> were obtained at the lowest operating temperatures of about 120 °C, which is typical for nanomaterials. Response (recovery) times to 400 ppb NO<sub>2</sub> were determined as a function of the operating temperature and indicated a significant decrease from 62 (42) s at 123 <b>°</b>C to 12 (19) s at 385 <b>°</b>C A much smaller sensitivity to H<sub>2</sub> was observed, which might be advantageous for selective detection of nitrogen oxides. The influence of humidity on the NO<sub>2</sub> response was demonstrated to be significantly below 150 <b>°</b>C and systematically decreased upon increase in the operating temperature up to 400 <b>°</b>C.
topic gas sensors
SnO2
TiO2
thin films
Langmuir-Blodgett technique
url https://www.mdpi.com/1424-8220/20/23/6830
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