Special Issue "Metal Oxide Films and Their Applications"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: 30 September 2021.

Special Issue Editor

Prof. Dr. Artur M. Rydosz
Website
Guest Editor
Department of Electronics, AGH University of Science and Technology, 30-059 Krakow, Poland
Interests: metal oxide thin films; nanomaterials; gas sensors; acetone detection; exhaled breath analysis
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

We would like to invite you to submit your work to this Special Issue entitled "Metal Oxide Films and Their Applications". Metal oxides have very different electrical properties from metals, semiconductors, and insulators, and are used in many different areas (e.g., gas sensors, optical devices). The ability of metal oxides to change their electrical conductivity with the composition of the surrounding atmosphere has been proven by researchers all over the world. This progress has been supported by the industrial development of novel characterization and deposition tools. The aim of this Special Issue is to present the latest experimental and theoretical developments in the field, through a combination of original research papers and review articles from leading groups around the world.

In particular, the topics of interest include, but are not limited to:

  • Gas-sensing applications;
  • Optical devices;
  • Electrochemical applications;
  • Theoretical studies of metal oxides;
  • The development of deposition techniques.

Dr. Artur M. Rydosz
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

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Open AccessArticle
Influence of GLAD Sputtering Configuration on the Crystal Structure, Morphology, and Gas-Sensing Properties of the WO3 Films
Coatings 2020, 10(11), 1030; https://doi.org/10.3390/coatings10111030 - 26 Oct 2020
Abstract
In this paper, we describe a deposition method and investigation of the physical properties of WO3 films. We investigated tungsten oxide due to its potential application as a gas sensor. Thin films of the WO3 were deposited on glass, silicon, and [...] Read more.
In this paper, we describe a deposition method and investigation of the physical properties of WO3 films. We investigated tungsten oxide due to its potential application as a gas sensor. Thin films of the WO3 were deposited on glass, silicon, and alumina substrates by magnetron GLAD sputtering. The crystallinity of films was determined by X-ray diffraction (XRD) and the thickness by X-Ray Reflectivity (XRR) and spectroscopic ellipsometry (SE). Surface morphology, which is important for gas sensitivity, was measured by atomic force microscopy (AFM). We studied the gas-sensing characteristics under exposure to acetone in the 0.1–1.25 ppm range which covers the levels of exhaled breath acetone. We show that WO3 sensors have different sensitivity for different sputter angle. Furthermore, we demonstrate the influence of temperature during gas content measurement. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Open AccessArticle
Multilayer Structure of Reduced Graphene Oxide and Copper Oxide as a Gas Sensor
Coatings 2020, 10(11), 1015; https://doi.org/10.3390/coatings10111015 - 22 Oct 2020
Cited by 2
Abstract
Reduced graphene oxide and copper oxide multilayer structures were fabricated in a planar configuration by deposition on both ceramic and Si/SiO2 substrates with interdigitated Au electrodes by the spray method. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (X-ray diffraction), and [...] Read more.
Reduced graphene oxide and copper oxide multilayer structures were fabricated in a planar configuration by deposition on both ceramic and Si/SiO2 substrates with interdigitated Au electrodes by the spray method. SEM (scanning electron microscopy), TEM (transmission electron microscopy), XRD (X-ray diffraction), and elemental analysis investigations indicated that graphene oxide (GO) was obtained in a form of interconnected flakes consisting of 6–7 graphene layers for GO with the total thickness of ca. 6 nm and 2–3 layers for rGO with the total thickness of 1 nm. The lateral size of one flake reached up to 10 micrometers. Copper oxide was obtained by the wet chemical method. The number of sequential layers of the sensing structure was optimized to obtain good sensitivity and acceptable response/recovery times in response to the oxidizing nitrogen dioxide atmosphere. Both semiconductor partners revealed p-type conductivity. Formation of isotype heterojunctions between both semiconductor partners was taken into account and their influence on electrical transport explained. Optimized sensor structures revealed relative sensitivities reaching several tens of percent and acceptable response and recovery times in NO2 concentration ranged from a few to 20 ppm. Possibility of manufacturing sensors working at room temperature was shown, but at the cost of prolonged response/recovery times. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Open AccessArticle
GLAD Magnetron Sputtered Ultra-Thin Copper Oxide Films for Gas-Sensing Application
Coatings 2020, 10(4), 378; https://doi.org/10.3390/coatings10040378 - 11 Apr 2020
Cited by 4
Abstract
Copper oxide (CuO) ultra-thin films were obtained using magnetron sputtering technology with glancing angle deposition technique (GLAD) in a reactive mode by sputtering copper target in pure argon. The substrate tilt angle varied from 45 to 85° and 0°, and the sample rotation [...] Read more.
Copper oxide (CuO) ultra-thin films were obtained using magnetron sputtering technology with glancing angle deposition technique (GLAD) in a reactive mode by sputtering copper target in pure argon. The substrate tilt angle varied from 45 to 85° and 0°, and the sample rotation at a speed of 20 rpm was stabilized by the GLAD manipulator. After deposition, the films were annealed at 400 °C/4 h in air. The CuO ultra-thin film structure, morphology, and optical properties were assessed by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray reflectivity (XRR), and optical spectroscopy. The thickness of the films was measured post-process using a profilometer. The obtained copper oxide structures were also investigated as gas-sensitive materials after exposure to acetone in the sub-ppm range. After deposition, gas-sensing measurements were performed at 300, 350, and 400 °C and 50% relative humidity (RH) level. We found that the sensitivity of the device is related to the thickness of CuO thin films, whereas the best results are obtained with an 8 nm thick sample. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Open AccessFeature PaperArticle
Synthesis of Nanoporous TiO2 with the Use of Diluted Hydrogen Peroxide Solution and Its Application in Gas Sensing
Coatings 2019, 9(10), 681; https://doi.org/10.3390/coatings9100681 - 19 Oct 2019
Cited by 3
Abstract
The chemical routes of metal oxidation in presence of hydrogen peroxide solutions are tailor-made for the synthesis of biocompatible metal oxide surfaces with clean intermediate and end products, such as oxides, hydroxides, hydrogen and water. The hydrolysis of titanium in hydrogen peroxide solutions [...] Read more.
The chemical routes of metal oxidation in presence of hydrogen peroxide solutions are tailor-made for the synthesis of biocompatible metal oxide surfaces with clean intermediate and end products, such as oxides, hydroxides, hydrogen and water. The hydrolysis of titanium in hydrogen peroxide solutions is particularly interesting for medical applications, forming micro- and nanoscale titania surfaces. In this paper, the content of the hydrolysis solution is revised, allowing the fabrication of gas sensor devices based on nanoporous titania. Nanopore and microcrack formations were discussed in detail by monitoring the structural changes on the thin film surface with field-emission scanning electron microscopy (FE-SEM). A stable rutile crystalline phase was detected by glancing incidence X-ray diffraction (GI-XRD) measurement after repetitive hydrothermal processes. Electrical conductance measurements were carried out at high temperatures (400–600 °C) under humid airflow (40% [email protected] °C) with the injection of various concentrations of a wide set of test compounds (C2H3N, CO, H2, NO2, C2H6O), to observe the sensing capabilities of the material. Furthermore, the humidity effects on the sensing properties toward H2, CO, and C2H6O have been discussed. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Review

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Open AccessFeature PaperReview
Semiconducting Metal Oxides: SrTiO3, BaTiO3 and BaSrTiO3 in Gas-Sensing Applications: A Review
Coatings 2021, 11(2), 185; https://doi.org/10.3390/coatings11020185 - 04 Feb 2021
Abstract
In this work, a broad overview in the field of strontium titanate (ST, SrTiO3)-, barium titanate (BT, BaTiO3)- and barium strontium titanate (BST, BaSrTiO3)-based gas sensors is presented and discussed. The above-mentioned materials are characterized by a [...] Read more.
In this work, a broad overview in the field of strontium titanate (ST, SrTiO3)-, barium titanate (BT, BaTiO3)- and barium strontium titanate (BST, BaSrTiO3)-based gas sensors is presented and discussed. The above-mentioned materials are characterized by a perovskite structure with long-term stability and therefore are very promising materials for commercial gas-sensing applications. Within the last 20 years, the number of papers where ST, BT and BST materials were tested as gas-sensitive materials has ten times increased and therefore an actual review about them in this field has been expected by readers, who are researchers involved in gas-sensing applications and novel materials investigations, as well as industry research and development center members, who are constantly searching for gas-sensing materials exhibiting high 3S parameters (sensitivity, selectivity and stability) that can be adapted for commercial realizations. Finally, the NO2-sensing characteristics of the BST-based gas sensors deposited by the authors with the utilization of magnetron sputtering technology are presented. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Open AccessReview
Preparation and Characterization of NbxOy Thin Films: A Review
Coatings 2020, 10(12), 1246; https://doi.org/10.3390/coatings10121246 - 17 Dec 2020
Abstract
Niobium oxides (NbO, NbO2, Nb2O5), being a versatile material has achieved tremendous popularity to be used in a number of applications because of its outstanding electrical, mechanical, chemical, and magnetic properties. NbxOy films possess [...] Read more.
Niobium oxides (NbO, NbO2, Nb2O5), being a versatile material has achieved tremendous popularity to be used in a number of applications because of its outstanding electrical, mechanical, chemical, and magnetic properties. NbxOy films possess a direct band gap within the ranges of 3.2–4.0 eV, with these films having utility in different applications which include; optical systems, stainless steel, ceramics, solar cells, electrochromic devices, capacitor dielectrics, catalysts, sensors, and architectural requirements. With the purpose of fulfilling the requirements of a vast variety of the named applications, thin films having comprehensive properties span described by film composition, morphology, structural properties, and thickness are needed. The theory, alongside the research status of the different fabrication techniques of NbxOy thin films are reported in this work. The impact of fabrication procedures on the thin film characteristics which include; film thickness, surface quality, optical properties, interface properties, film growth, and crystal phase is explored with emphases on the distinct deposition process applied, are also described and discussed. Full article
(This article belongs to the Special Issue Metal Oxide Films and Their Applications)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Semiconducting metal oxides: SrTiO3, BaTiO3, and BaSrTiO3 in gas-sensing applications.
Authors: Bartłomiej Szafraniak, Łukasz Fuśnik, Jie Xu, Feng Gao, Artur Rydosz*
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