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Structural, Morphological, and Optical Properties of Functional 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 (20 June 2023) | Viewed by 11834

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Guest Editor
Science Faculty, Department of Physics, University of Craiova, 200585 Craiova, Romania
Interests: thin films; pulsed laser deposition (PLD); structural and optical characterization of materials; PLD plasma emission characterisation
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Guest Editor
National Institute for Research & Development in Chemistry and Petrochemistry-ICECHIM, 202 Spl. Independentei, 060021 Bucharest, Romania
Interests: polymer science; polymer processing; thermoplastics; composites and nanocomposites; bio-based thermoplastics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Thin films by pulsed laser deposition evolved fast in the last years, towards high interdisciplinary research, using new classes of materials with different particularities in their interaction with plasma and use in ablative process. Thin films based on new metal oxides, nanoparticles or 2D structures evolved fast, materials for sensors, doping sensors, polymer assisted or different polymer composites and nanocomposites for multifunctional structures, allowed a wide spectrum of use in applications from quantum effects to sensing, actuators, photovoltaics, plasmon assisted process, new target materials for PLD process able to offer tailored properties, advanced materials for biomedical applications, lab on chip applications, high secure inscription process, superconductive materials, semiconductors, self-assembling using block copolymers, porous structures and many others. Such materials due their outstanding properties can bring advances in electronics, biochemistry, environmental sciences, energy, biomedicine, automotive, aerospace (but limited to), by integrating different materials and components with the processing technology. The special issue should be focused also on the physical and chemical absorbance of the toxic gases on the surface and the modification of the surface.

Dr. Mariana Osiac
Dr. Mihai Cosmin Corobea
Guest Editors

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Keywords

  • sensors
  • polymer composites and nanocomposites
  • nanoparticles
  • metal oxides

Published Papers (7 papers)

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Research

12 pages, 5429 KiB  
Article
Exploring Pyrrolo-Phenanthrolines as Semiconductors for Potential Implementation in Organic Electronics
by Corneliu Doroftei, Liviu Leontie, Ramona Danac, Cristina-Maria Al Matarneh and Aurelian Carlescu
Materials 2023, 16(9), 3366; https://doi.org/10.3390/ma16093366 - 25 Apr 2023
Viewed by 886
Abstract
This paper describes the synthesis and characterization of new organic semiconductors based on pyrrolo[1,2-i][1,7]phenanthrolines in the form of thin layers. The thin layers, produced via the spin coating method (with a thickness of 10–11 μm), were investigated for their electrical and optical properties. [...] Read more.
This paper describes the synthesis and characterization of new organic semiconductors based on pyrrolo[1,2-i][1,7]phenanthrolines in the form of thin layers. The thin layers, produced via the spin coating method (with a thickness of 10–11 μm), were investigated for their electrical and optical properties. After heat treatment at temperatures ranging from 210 to 240 °C, the layers displayed consistent and reproducible properties. The layers exhibited n-type semiconductor behavior, with a thermal activation energy (Ea) in the range of 0.75–0.78 eV. Additionally, the layers showed transmittance values of 84–92% in the visible and near-infrared spectral ranges, with a direct optical band gap (Egod) ranging from 3.13 to 4.11 eV. These thin layers have potential applications in electronic devices such as thermistors, as well as in nanoelectronics and optoelectronics. Overall, these new organic semiconductors show promising properties for practical implementation in various electronic applications. Full article
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13 pages, 3392 KiB  
Article
Plasmonic Perfect Absorber Utilizing Polyhexamethylene Biguanide Polymer for Carbon Dioxide Gas Sensing Application
by Muhammad Irfan, Yousuf Khan, Atiq Ur Rehman, Naqeeb Ullah, Svetlana N. Khonina, Nikolay L. Kazanskiy and Muhammad A. Butt
Materials 2023, 16(7), 2629; https://doi.org/10.3390/ma16072629 - 26 Mar 2023
Cited by 3 | Viewed by 1476
Abstract
In this paper a perfect absorber with a photonic crystal cavity (PhC-cavity) is numerically investigated for carbon dioxide (CO2) gas sensing application. Metallic structures in the form of silver are introduced for harnessing plasmonic effects to achieve perfect absorption. The sensor [...] Read more.
In this paper a perfect absorber with a photonic crystal cavity (PhC-cavity) is numerically investigated for carbon dioxide (CO2) gas sensing application. Metallic structures in the form of silver are introduced for harnessing plasmonic effects to achieve perfect absorption. The sensor comprises a PhC-cavity, silver (Ag) stripes, and a host functional material—Polyhexamethylene biguanide polymer—deposited on the surface of the sensor. The PhC-cavity is implemented within the middle of the cell, helping to penetrate the EM waves into the sublayers of the structure. Therefore, corresponding to the concentration of the CO2 gas, as it increases, the refractive index of the host material decreases, causing a blue shift in the resonant wavelength and vice versa of the device. The sensor is used for the detection of 0–524 parts per million (ppm) concentration of the CO2 gas, with a maximum sensitivity of 17.32 pm (pico meter)/ppm achieved for a concentration of 366 ppm with a figure of merit (FOM) of 2.9 RIU−1. The four-layer device presents a straightforward and compact design that can be adopted in various sensing applications by using suitable host functional materials. Full article
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8 pages, 722 KiB  
Article
Wet-Oxidation-Assisted Chemical Mechanical Polishing and High-Temperature Thermal Annealing for Low-Loss 4H-SiC Integrated Photonic Devices
by Xiaodong Shi, Yaoqin Lu, Didier Chaussende, Karsten Rottwitt and Haiyan Ou
Materials 2023, 16(6), 2324; https://doi.org/10.3390/ma16062324 - 14 Mar 2023
Cited by 1 | Viewed by 1517
Abstract
Silicon carbide (SiC) has become a promising optical material for quantum photonics and nonlinear photonics during the past decade. In this work, we propose two methods to improve the 4H-SiC thin film quality for SiC integrated photonic chips. Firstly, we develop a wet-oxidation-assisted [...] Read more.
Silicon carbide (SiC) has become a promising optical material for quantum photonics and nonlinear photonics during the past decade. In this work, we propose two methods to improve the 4H-SiC thin film quality for SiC integrated photonic chips. Firstly, we develop a wet-oxidation-assisted chemical mechanical polishing (CMP) process for 4H-SiC, which can significantly decrease the surface roughness from 3.67 nm to 0.15 nm, thus mitigating the light scattering loss. Secondly, we find that the thermal annealing of the 4H-SiC devices at 1300 °C can help to decrease the material absorption loss. We experimentally demonstrate that the wet-oxidation-assisted CMP and the high-temperature annealing can effectively increase the intrinsic quality factor of the 4H-SiC optical microring resonators. Full article
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14 pages, 7008 KiB  
Article
Silver Nanoparticles for Fluorescent Nanocomposites by High-Pressure Magnetron Sputtering
by Tomáš Zikmund, Jiří Bulíř, Michal Novotný, Ladislav Fekete, Sergii Chertopalov, Stefan Andrei Irimiciuc, Mariana Klementová, Jarmila Balogová and Jan Lančok
Materials 2023, 16(4), 1591; https://doi.org/10.3390/ma16041591 - 14 Feb 2023
Cited by 2 | Viewed by 1461
Abstract
We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles [...] Read more.
We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles were characterized by scanning and transmission electron microscopy and spectral ellipsometry. The physical shape of the nanoparticles and its distribution was correlated with their optical properties. Metal–dielectric nanocomposites were deposited employing simultaneous deposition of Ag NPs via high-pressure magnetron sputtering and the dielectric matrix was deposited via thermal evaporation. Pure and Eu-, Er-, and Yb-doped lithium fluoride was used as the dielectric host matrix. Optical transmittance of lithium fluoride containing silver nanoparticles was measured and their theoretical absorption cross-section calculated. The nanoparticles were also embedded in Eu3+-doped downshifting and Er3+- and Yb3+-doped up-conversion materials to study their influence on emission spectra. Spectra of identical layers with and without nanoparticles were compared. Their transmittance at various annealing temperatures is also presented. Full article
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14 pages, 4604 KiB  
Article
Towards Room Temperature Phase Transition of W-Doped VO2 Thin Films Deposited by Pulsed Laser Deposition: Thermochromic, Surface, and Structural Analysis
by Yannick Bleu, Florent Bourquard, Vincent Barnier, Anne-Sophie Loir, Florence Garrelie and Christophe Donnet
Materials 2023, 16(1), 461; https://doi.org/10.3390/ma16010461 - 03 Jan 2023
Cited by 8 | Viewed by 2856
Abstract
Vanadium dioxide (VO2) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W [...] Read more.
Vanadium dioxide (VO2) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W doping on the thermochromic, surface, and nanostructure properties of VO2 thin film was investigated in the present proof. W-doped VO2 thin films with different W contents were deposited by pulsed laser deposition (PLD) using V/W (+O2) and V2O5/W multilayers. Rapid thermal annealing at 400–450 °C under oxygen flow was performed to crystallize the as-deposited films. The thermochromic, surface chemistry, structural, and morphological properties of the thin films obtained were investigated. The results showed that the V5+ was more surface sensitive and W distribution was homogeneous in all samples. Moreover, the V2O5 acted as a W diffusion barrier during the annealing stage, whereas the V+O2 environment favored W surface diffusion. The phase transition temperature gradually decreased with increasing W content with a high efficiency of −26 °C per at. % W. For the highest doping concentration of 1.7 at. %, VO2 showed room-temperature transition (26 °C) with high luminous transmittance (62%), indicating great potential for optical applications. Full article
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26 pages, 8095 KiB  
Article
Deposition of Sol–Gel ZnO:Mg Films and Investigation of Their Structural and Optical Properties
by Tatyana Ivanova, Antoaneta Harizanova, Tatyana Koutzarova, Benedicte Vertruyen and Raphael Closset
Materials 2022, 15(24), 8883; https://doi.org/10.3390/ma15248883 - 12 Dec 2022
Cited by 7 | Viewed by 1698
Abstract
This work presents a facile sol–gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 and 3 wt%) and post-annealing treatments (300–600 °C) on [...] Read more.
This work presents a facile sol–gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 and 3 wt%) and post-annealing treatments (300–600 °C) on the film’s structural, vibrational and optical properties is investigated. Undoped ZnO films crystallize in the wurtzite phase, with crystallite sizes ranging from 9.1 nm (300 °C) to 29.7 nm (600 °C). Mg doping deteriorates the film crystallization and shifting of 002 peak towards higher diffraction angles is observed, indicating the successful incorporation of Mg into the ZnO matrix. ZnO:Mg films (2 wt%) possess the smallest crystallite size, ranging from 6.2 nm (300 °C) to 25.2 nm (600 °C). The highest Mg concentration (3 wt%) results into a segregation of the MgO phase. Lattice constants, texture coefficients and Zn–O bond lengths are discussed. The diminution of the c lattice parameter is related to the replacement of Zn2+ by Mg2+ in the ZnO host lattice. The vibrational properties are studied by Fourier transform infrared (FTIR) spectroscopy. IR lines related to Mg–O bonds are found for ZnO:Mg films with dopant concentrations of 2 and 3 wt%. The optical characterization showed that the transmittance of ZnO:Mg thin films increased from 74.5% (undoped ZnO) to about 89.1% and the optical band gap energy from 3.24 to 3.56 eV. Mg doping leads to a higher refractive index compared to undoped ZnO films. The FESEM (field emission scanning electron microscopy) technique is used for observation of the surface morphology modification of ZnO:Mg films. The doped ZnO films possess a smoother grained surface structure, opposite to the wrinkle-type morphology of undoped sol–gel ZnO films. The smoother surface leads to improved transparency of ZnO:Mg films. Full article
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12 pages, 2092 KiB  
Article
Hybrid Dispersion Model Characterization of PAZO Azopolymer Thin Films over the Entire Transmittance Spectrum Measured in the UV/VIS/NIR Spectral Region
by Dorian Minkov, Lian Nedelchev, George Angelov, Emilio Marquez, Blaga Blagoeva, Georgi Mateev and Dimana Nazarova
Materials 2022, 15(23), 8617; https://doi.org/10.3390/ma15238617 - 02 Dec 2022
Cited by 3 | Viewed by 1164
Abstract
Notwithstanding the significant optical applicability of PAZO polymer films, there are no accurate data about their optical characteristics. To remedy this shortcoming, in this study three PAZO polymer thin films are characterized, with dissimilar thicknesses, on glass substrates using only one UV/VIS/NIR transmittance [...] Read more.
Notwithstanding the significant optical applicability of PAZO polymer films, there are no accurate data about their optical characteristics. To remedy this shortcoming, in this study three PAZO polymer thin films are characterized, with dissimilar thicknesses, on glass substrates using only one UV/VIS/NIR transmittance spectrum T(λ) per sample and an original hybrid dispersion model (HDM). HDM is based on the Tauc–Lorentz model, the new amorphous dispersion formula, the Tauc–Lorentz–Urbach model of Foldyna and the Tauc–Lorentz–Urbach model of Rodriguez. HDM with two oscillators is employed in characterizations of the PAZO polymer films in the range [300, 2500] nm, whereby the root-mean-square deviation (RMSD) of the fitted transmittance spectrum with respect to T(λ) does not exceed 1.6 × 10−3. Decreasing RMSD by 2.3% to 94.4% is demonstrated by employing HDM compared with the above mentioned four popular dispersion models, for each one of the studied films. HDM is applicable to amorphous films independent of their thickness as well as to cases of non-transparent substrate. Full article
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