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Optical Characterization and Applications of Metallic Thin Films

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Thin Films and Interfaces".

Deadline for manuscript submissions: closed (10 August 2022) | Viewed by 17742

Special Issue Editor

Institute of Mathematics and Physics, UTP University of Science and Technology, Kaliskiego 7, 85-796 Bydgoszcz, Poland
Interests: optical properties; microstructure; spectroscopic ellipsometry; functional coatings
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Metallic thin films are important parts of various devices used in microelectronics and optoelectronics. Noble metals (NM) are used as a conducting layer between oxide films (e.g., ZnO/Ag/ZnO) and as a replacement for transparent conductive oxides (TSOs). These structures exhibit high conductivity and enough transmission in the visible spectral range, and they are suitable for use on flexible substrates. NM-alloys (i.e., Ag–Sn/In, Cu–Sn/In, Au–Sn/In) connect low electric resistivity of noble metal with a low melting temperature of Sn or In. Obviously, we cannot forget about the plasmonic effects of metallic thin films which are utilized in, e.g., optical sensors. The sensing mechanism of such a system is based on two phenomena: surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR). In SPR and LSPR, the optical constants of metallic films (and surrounding medium), which strongly depend on growing conditions, are crucial parameters affecting the operation of the system.

The aim of this Special Issue of Materials is to present the optical properties of metallic thin films (single layers of metals or alloys, multilayer systems or structures with metallic layers) which can be used is micro- and optoelectronics.

Dr. Lukasz Skowronski
Guest Editor

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Keywords

  • Metallic thin films
  • Noble metals
  • Alloys
  • Optical properties
  • Optical constants
  • SPR
  • LSPR
  • Plasmonics
  • Microstructure

Published Papers (8 papers)

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Research

12 pages, 2083 KiB  
Article
Influence of Thin Film Deposition on AFM Cantilever Tips in Adhesion and Young’s Modulus of MEMS Surfaces
by Pedram Heidari, Majid Salehi, Behrooz Ruhani, Violeta Purcar and Simona Căprărescu
Materials 2022, 15(6), 2102; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062102 - 12 Mar 2022
Cited by 7 | Viewed by 2275
Abstract
Adhesion is a critical factor in microelectromechanical systems (MEMSs) and is influenced by many parameters. In important fields, such as microassembly, an improved understanding of adhesion can result in higher precision. This study examines the influence of deposition of gold and titanium onto [...] Read more.
Adhesion is a critical factor in microelectromechanical systems (MEMSs) and is influenced by many parameters. In important fields, such as microassembly, an improved understanding of adhesion can result in higher precision. This study examines the influence of deposition of gold and titanium onto the atomic force microscope (AFM) tips in adhesion forces and Young’s modulus, between a few MEMS substrates (silicon, gold, and silver) and the AFM tips. It was found that, except for gold substrate, an AFM tip coated with gold has the highest adhesion force of 42.67 nN for silicon substrates, whereas the titanium-coated AFM tip decreases the force for all the samples. This study suggests that such changes must be taken into account while studying the adhesion force. The final results indicate that utilizing gold substrate with titanium AFM tip led to the lowest adhesion force, which could be useful in adhesion force measurement during microassembly. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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11 pages, 2961 KiB  
Article
Influence of the Microstructure and Optical Constants on Plasmonic Properties of Copper Nanolayers
by Tomasz Rerek, Beata Derkowska-Zielinska, Marek Trzcinski, Robert Szczesny, Mieczyslaw K. Naparty and Lukasz Skowronski
Materials 2021, 14(23), 7292; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14237292 - 29 Nov 2021
Viewed by 1235
Abstract
Copper layers with thicknesses of 12, 25, and 35 nm were thermally evaporated on silicon substrates (Si(100)) with two different deposition rates 0.5 and 5.0 Å/s. The microstructure of produced coatings was studied using atomic force microscopy (AFM) and [...] Read more.
Copper layers with thicknesses of 12, 25, and 35 nm were thermally evaporated on silicon substrates (Si(100)) with two different deposition rates 0.5 and 5.0 Å/s. The microstructure of produced coatings was studied using atomic force microscopy (AFM) and powder X-ray diffractometer (XRD). Ellipsometric measurements were used to determine the effective dielectric functions <ε˜> as well as the quality indicators of the localized surface plasmon (LSP) and the surface plasmon polariton (SPP). The composition and purity of the produced films were analysed using X-ray photoelectron spectroscopy (XPS). Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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15 pages, 2178 KiB  
Article
Microstructure and Optical Properties of Nanostructural Thin Films Fabricated through Oxidation of Au–Sn Intermetallic Compounds
by Lukasz Skowronski, Marek Trzcinski, Aleksandra Olszewska and Robert Szczesny
Materials 2021, 14(14), 4034; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14144034 - 19 Jul 2021
Cited by 7 | Viewed by 2157
Abstract
AuSn and AuSn2 thin films (5 nm) were used as precursors during the formation of semiconducting metal oxide nanostructures on a silicon substrate. The nanoparticles were produced in the processes of annealing and oxidation of gold–tin intermetallic compounds under ultra-high vacuum conditions. [...] Read more.
AuSn and AuSn2 thin films (5 nm) were used as precursors during the formation of semiconducting metal oxide nanostructures on a silicon substrate. The nanoparticles were produced in the processes of annealing and oxidation of gold–tin intermetallic compounds under ultra-high vacuum conditions. The formation process and morphology of a mixture of SnO2 and Au@SnOx (the core–shell structure) nanoparticles or Au nanocrystalites were carefully examined by means of spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX). The annealing and oxidation of the thin film of the AuSn intermetallic compound led to the formation of uniformly distributed structures with a size of ∼20–30 nm. All of the synthesized nanoparticles exhibited a strong absorption band at 520–530 nm, which is typical for pure metallic or metal oxide systems. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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12 pages, 8232 KiB  
Article
Synthesis of Copper Nitride Layers by the Pulsed Magnetron Sputtering Method Carried out under Various Operating Conditions
by Magdalena Wilczopolska, Katarzyna Nowakowska-Langier, Sebastian Okrasa, Lukasz Skowronski, Roman Minikayev, Grzegorz W. Strzelecki, Rafal Chodun and Krzysztof Zdunek
Materials 2021, 14(10), 2694; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14102694 - 20 May 2021
Cited by 11 | Viewed by 2220
Abstract
Copper nitride shows various properties that depend on the structure of the material and is influenced by the change in technical parameters. In the present work, Cu–N layers were synthesized using the pulsed magnetron sputtering method. The synthesis was performed under different operating [...] Read more.
Copper nitride shows various properties that depend on the structure of the material and is influenced by the change in technical parameters. In the present work, Cu–N layers were synthesized using the pulsed magnetron sputtering method. The synthesis was performed under different operating conditions: direct current (DC) or alternating current (AC) power supply, and various atmospheres: pure Ar and a mixture of Ar + N2. The structural properties of the deposited layers were characterized by X-ray diffraction measurements, and Raman spectroscopy and scanning electron microscopy have been performed. Optical properties were also evaluated. The obtained layers showed tightly packed columnar grain features. The kinetics of the layer growth in the AC mode was lower than that observed in the DC mode, and the layers were thinner and more fine-grained. The copper nitride layers were characterized by the one-phase and two-phase polycrystalline structure of the Cu3N phase with the preferred growth orientation (100). The lattice constant oscillates between 3.808 and 3.815 Å for one-phase and has a value of 3.828 Å for a two-phase structure. Phase composition results were correlated with Raman spectroscopy measurements. Raman spectra exhibited a broad, diffused, and intense signal of Cu3N phase, with Raman shift located at 628–635 cm−1. Studies on optical properties showed that the energy gap ranged from 2.17 to 2.47 eV. The results showed that controlling technical parameters gives a possibility to optimize the structure and phase composition of deposited layers. The reported changes were discussed and attributed to the properties of the material layers and technology method. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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13 pages, 3693 KiB  
Article
Effects of Deposition and Annealing Temperature on the Structure and Optical Band Gap of MoS2 Films
by Gongying Chen, Benchu Lu, Xinyu Cui and Jianrong Xiao
Materials 2020, 13(23), 5515; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13235515 - 03 Dec 2020
Cited by 18 | Viewed by 2127
Abstract
In this study, molybdenum disulfide (MoS2) film samples were prepared at different temperatures and annealed through magnetron sputtering technology. The surface morphology, crystal structure, bonding structure, and optical properties of the samples were characterized and analyzed. The surface of the MoS [...] Read more.
In this study, molybdenum disulfide (MoS2) film samples were prepared at different temperatures and annealed through magnetron sputtering technology. The surface morphology, crystal structure, bonding structure, and optical properties of the samples were characterized and analyzed. The surface of the MoS2 films prepared by radio frequency magnetron sputtering is tightly coupled and well crystallized, the density of the films decreases, and their voids and grain size increase with the increase in deposition temperature. The higher the deposition temperature is, the more stable the MoS2 films deposited will be, and the 200 °C deposition temperature is an inflection point of the film stability. Annealing temperature affects the structure of the films, which is mainly related to sulfur and the growth mechanism of the films. Further research shows that the optical band gaps of the films deposited at different temperatures range from 0.92 eV to 1.15 eV, showing semiconductor bandgap characteristics. The optical band gap of the films deposited at 200 °C is slightly reduced after annealing in the range of 0.71–0.91 eV. After annealing, the optical band gap of the films decreases because of the two exciton peaks generated by the K point in the Brillouin zone of MoS2. The blue shift of the K point in the Brillouin zone causes a certain change in the optical band gap of the films. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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11 pages, 3994 KiB  
Article
Preparation of Copper Nitride Films with Superior Photocatalytic Activity through Magnetron Sputtering
by Aihua Jiang, Hongjuan Shao, Liwen Zhu, Songshan Ma and Jianrong Xiao
Materials 2020, 13(19), 4325; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13194325 - 28 Sep 2020
Cited by 9 | Viewed by 2155
Abstract
TiO2 possesses a wide forbidden band of about 3.2 eV, which severely limits its visible light absorption efficiency. In this work, copper nitride (Cu3N) films were prepared by magnetron sputtering at different gas flow ratios. The structure of the films [...] Read more.
TiO2 possesses a wide forbidden band of about 3.2 eV, which severely limits its visible light absorption efficiency. In this work, copper nitride (Cu3N) films were prepared by magnetron sputtering at different gas flow ratios. The structure of the films was tested by scanning electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscope. Optical properties were investigated by UV-vis spectrophotometer and fluorescence spectrometer. Results show that the Cu3N crystal possesses a typical anti-ReO3 crystal structure, and the ratio of nitrogen and Cu atoms of the Cu3N films was adjusted by changing the gas flow ratio. The Cu3N films possess an optical band gap of about 2.0 eV and energy gap of about 2.5 eV and exhibit excellent photocatalytic activity for degrading methyl orange (degradation ratio of 99.5% in 30 min). The photocatalytic activity of Cu3N mainly originates from vacancies in the crystal and Cu self-doping. This work provides a route to broaden the forbidden band width of photocatalytic materials and increase their photoresponse range. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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13 pages, 3866 KiB  
Article
Laser-Assisted Synthesis and Oxygen Generation of Nickel Nanoparticles
by Jakub Wawrzyniak, Jakub Karczewski, Jacek Ryl, Katarzyna Grochowska and Katarzyna Siuzdak
Materials 2020, 13(18), 4068; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13184068 - 13 Sep 2020
Cited by 4 | Viewed by 2149
Abstract
Nowadays, more than ever, environmental awareness is being taken into account when it comes to the design of novel materials. Herein, the pathway to the creation of a colloid of spherical, almost purely metallic nickel nanoparticles (NPs) through pulsed laser ablation in ethanol [...] Read more.
Nowadays, more than ever, environmental awareness is being taken into account when it comes to the design of novel materials. Herein, the pathway to the creation of a colloid of spherical, almost purely metallic nickel nanoparticles (NPs) through pulsed laser ablation in ethanol is presented. A complex description of the colloid is provided through UV-vis spectroscopy and dynamic light scattering analysis, ensuring insight into laser-induced nanoparticle homogenization and size-control of the NPs. The transmission electron spectroscopy revealed spherical nanoparticles with a narrow size distribution, whereas the energy-dispersive X-ray spectroscopy accompanied by the X-ray photoelectron spectroscopy revealed their metallic nature. Furthermore, an example of the application of the colloidal nanoparticles is presented, where a quick, five-min ultrasound modification results in over an order of magnitude higher current densities in the titania-based electrode for the oxygen evolution reaction. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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9 pages, 3288 KiB  
Article
Preparation of Cu3N/MoS2 Heterojunction through Magnetron Sputtering and Investigation of Its Structure and Optical Performance
by Liwen Zhu, Xiu Cao, Chenyang Gong, Aihua Jiang, Yong Cheng and Jianrong Xiao
Materials 2020, 13(8), 1873; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13081873 - 16 Apr 2020
Cited by 17 | Viewed by 2704
Abstract
Cu3N/MoS2 heterojunction was prepared through magnetron sputtering, and its optical band gap was investigated. Results showed that the prepared Cu3N/MoS2 heterojunction had a clear surface heterojunction structure, uniform surface grains, and no evident cracks. The optical band [...] Read more.
Cu3N/MoS2 heterojunction was prepared through magnetron sputtering, and its optical band gap was investigated. Results showed that the prepared Cu3N/MoS2 heterojunction had a clear surface heterojunction structure, uniform surface grains, and no evident cracks. The optical band gap (1.98 eV) of Cu3N/MoS2 heterojunction was obtained by analyzing the ultraviolet-visible transmission spectrum. The valence and conduction band offsets of Cu3N/MoS2 heterojunction were 1.42 and 0.82 eV, respectively. The Cu3N film and multilayer MoS2 formed a type-II heterojunction. After the two materials adhered to form the heterojunction, the interface electrons flowed from MoS2 to Cu3N because the latter had higher Fermi level than the former. This behavior caused the formation of additional electrons in the Cu3N and MoS2 layers and the change in optical band gap, which was conducive to the charge separation of electrons in MoS2 or MoS2 holes. The prepared Cu3N/MoS2 heterojunction has potential application in various high-performance photoelectric devices, such as photocatalysts and photodetectors. Full article
(This article belongs to the Special Issue Optical Characterization and Applications of Metallic Thin Films)
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