Editorial

0 pages, 190 KiB

Open AccessEditorial

Special Issue: Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation

by Imogen Birney

Coatings 2020, 10(12), 1228; https://doi.org/10.3390/coatings10121228 - 16 Dec 2020

Cited by 5 | Viewed by 2570

Today, thin films are near-ubiquitous and are utilised in a very wide range of industrially and scientifically important areas [...] Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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15 pages, 8462 KiB

Open AccessArticle

Multiscale Simulation of Shot-Peening-Assisted Low-Pressure Cold Spraying Based on Al-Zn-Al₂O₃ Coatings

by Kaoshi Zhang, Yanqiao Song, Shun Cai, Ziyu Wang, Wenliang Chen and Lingling Xie

Coatings 2022, 12(10), 1490; https://doi.org/10.3390/coatings12101490 - 07 Oct 2022

Cited by 2 | Viewed by 1440

Abstract

Low-pressure cold spraying has gained much significance for its good economy in recent years. However, compared with high-pressure cold spraying, the unsatisfactory performance of coatings prepared by this method is a key problem restricting its further development. To improve the properties of the [...] Read more.

Low-pressure cold spraying has gained much significance for its good economy in recent years. However, compared with high-pressure cold spraying, the unsatisfactory performance of coatings prepared by this method is a key problem restricting its further development. To improve the properties of the coating without incorporating severe conditions, the paper proposed an original shot-peening-assisted low-pressure cold-spraying method (i.e., SP-LPCS). By proceeding with cold spraying and shot peening alternately, SP-LPCS was proved to enhance the mechanical property of the coating effectively. Mixed particles of Zn, Al, and Al₂O₃ were adopted as the coating powder. Effects of shot-peening pressure, flow rate, and shot size on the micromorphology and the microhardness variance were studied. Results shows that the thickness of the plastic deformation layer stabilizes as the impact time increases to 6. The microscopic simulation of the deformation shows that according to the different metal characteristics of the powder, brittle grains fracture while plastic grains go through deformation and refinement. Meanwhile, the porosity decreases greatly after the impacts, resulting in a higher denseness of the coating. Several factors mutually contribute to the performance improvement of the coating. The microhardness of the material was increased after SP-LPCS, and obvious strengthening belts were observed, with the highest microhardness being 90.93Hv. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation II)

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7 pages, 1792 KiB

Open AccessArticle

Growth of Highly Transparent Amorphous Carbon Films Using Beam Plasma Source

by Youngsuk Kim, Nina Baule, Maheshwar Shrestha and Qi Hua Fan

Coatings 2022, 12(8), 1159; https://doi.org/10.3390/coatings12081159 - 11 Aug 2022

Viewed by 1580

Abstract

A single beam plasma source was used to deposit hydrogenated amorphous carbon (a-C:H) coatings at room temperature. Using methane source gas, a-C:H coatings were deposited at different radio frequency (RF) power to fabricate transparent and durable coatings. The film deposition rate was almost [...] Read more.

A single beam plasma source was used to deposit hydrogenated amorphous carbon (a-C:H) coatings at room temperature. Using methane source gas, a-C:H coatings were deposited at different radio frequency (RF) power to fabricate transparent and durable coatings. The film deposition rate was almost linearly proportional to the ion source power. Hydrogenated amorphous carbon films of ~100 nm thickness appeared to be highly transparent from UV to the infrared range with a transmittance of ~90% and optical bandgap of ~3.7 eV. The coatings also possess desirable mechanical properties with Young’s modulus of ~78 GPa and density of ~1.9 g/cm³. The combined material properties of high transmittance and high durability make the ion-source-deposited a-C:H coatings attractive for many applications. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation II)

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8 pages, 1713 KiB

Open AccessArticle

Research on Fabrication Techniques and Focusing Characteristics of Metalens

by Yuhui Zhang, Yuegang Fu, Chenhao Ma, Bowei Yang and Yuanzhi Zhao

Coatings 2022, 12(3), 359; https://doi.org/10.3390/coatings12030359 - 08 Mar 2022

Cited by 3 | Viewed by 2172

Abstract

Metalenses have recently attracted increased attention due to their remarkable characteristics. The fabrication technology of metalenses has also become an important research direction. In this study, we propose a metalens structure based on Au–MgF₂–Au in infrared waveband. The preparation process of [...] Read more.

Metalenses have recently attracted increased attention due to their remarkable characteristics. The fabrication technology of metalenses has also become an important research direction. In this study, we propose a metalens structure based on Au–MgF₂–Au in infrared waveband. The preparation process of the metalens included magnetron sputtering, electron beam evaporation, and electron beam exposure. A dose test was performed during the exposure process, adjusting the exposure dose to minimize the proximity effect after exposure. Then, SEM was used to measure the processed metalens structure, and FDTD software was used to build a model based on the metalens, simulating and analyzing its focusing characteristics. The results show that the size deviation produced during the processing has little effect on the functionality of the metalens. The processed metalens can also focus different polarized light incidences at different spatial positions: The metalens can focus at 4.97 μm for x-polarized light and focus at 13.5 μm for y-polarized light. Additionally, the metalens has good focusing effects with different working wavelengths. We believe that the processing method of metalens proposed in this paper provides guidance for the preparation of subwavelength metasurface structures, and our findings are beneficial in developing new methods of near-infrared regime manipulation. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation II)

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13 pages, 6387 KiB

Open AccessArticle

Design and Fabrication of an Integrated Dual-Channel Thin-Film Filter for the Mid-Infrared

by Shun Zhou, Liyu Zhang, Feng Guo, Chunfang Wu, Junqi Xu, Kaifeng Zhang, Kun Li, Zheng Liu, Xiangguo Xiao, Shigeng Song and Weiguo Liu

Coatings 2021, 11(7), 803; https://doi.org/10.3390/coatings11070803 - 02 Jul 2021

Cited by 8 | Viewed by 2735

Abstract

Micro-filters fabricated using integration methods is now the trend for multichannel filters in imaging spectrum systems. Traditional multichannel bandpass filters are mainly fabricated separately by multilayered thin films and then glued together. This approach involves the complexity of precision cutting, dicing, and adhesive [...] Read more.

Micro-filters fabricated using integration methods is now the trend for multichannel filters in imaging spectrum systems. Traditional multichannel bandpass filters are mainly fabricated separately by multilayered thin films and then glued together. This approach involves the complexity of precision cutting, dicing, and adhesive bonding; therefore, the possibility of miniaturization is quite limited. In this work, a dual channel bandpass thin film filter for the mid-infrared was fabricated by using the lift-off process. The structure of a 4-cavity Fabray–Perot (F-P) type filter was designed and optimized. The bandpass filter over the range 3.55–3.75 µm with full width at half maximum (FWHM) of 274 nm and the bandpass filter over the range 4.85–4.95 µm with FWHM of 246 nm were obtained with a 4.5 µm joint width. The average transmittance of the filters is more than 83.5% and optical density value of the cutoff is 3. The thickness of 3.55–3.75 µm bandpass filter was measured and the thickness error was analyzed. The results show that the thickness error, especially the thickness error of spacer layers, induces the degradations of peak transmission and bandwidth. This kind of mid-infrared filter has important application in space remote sensing, military, and civil fields. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation II)

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15 pages, 13658 KiB

Open AccessArticle

Modeling and Experimental Investigations of Nanostructured Ag Thin Films Produced by Oblique-Angle Deposition and Its SERS Performance

by Datai Hui, Shun Zhou, Changlong Cai, Shigeng Song, Zhentao Wu, Jian Song, Da Zhang, Xiao Meng, Bo Lu, Yingbu Duan, Hayrigul Tursun and Des Gibson

Coatings 2021, 11(4), 458; https://doi.org/10.3390/coatings11040458 - 15 Apr 2021

Cited by 2 | Viewed by 2320

Abstract

The growth mechanism of nanocolumnar silver thin film deposited on a smooth silicon substrate using electron beam evaporation process at an oblique angle was simulated with the Kinetic Monte Carlo method. Following the simulated silver nanostructured thin film, a further computational simulation was [...] Read more.

The growth mechanism of nanocolumnar silver thin film deposited on a smooth silicon substrate using electron beam evaporation process at an oblique angle was simulated with the Kinetic Monte Carlo method. Following the simulated silver nanostructured thin film, a further computational simulation was done using COMSOL for surface-enhanced Raman scattering effects. The simulation results were compared against corresponding experimental results, which demonstrated high agreement between simulation results and experimental data. It was found that as the incident deposition angle increased, the density of the Ag thin film significantly decreased and the surface roughness increased. When the incident deposition angle was at 75° and 85°, the resulting nanocolumnar structure was significantly tilted. For Ag thin films deposited at all investigated angles, surface-enhanced Raman scattering effects were observed. Particularly, the Ag nanocolumns deposited at 85° showed remarkable Surface-enhanced Raman Scattering effects. This was seen in both COMSOL simulations and experimental results: Enhancement factors were 2 × 10⁷ in COMSOL simulation and 3.3 × 10⁵ in the experiment. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation II)

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13 pages, 8974 KiB

Open AccessArticle

Improvement of the Interfacial Fatigue Strength and Milling Behavior of Diamond Coated Tools via Appropriate Annealing

by Georgios Skordaris, Tilemachos Kotsanis, Apostolos Boumpakis and Fani Stergioudi

Coatings 2020, 10(9), 821; https://doi.org/10.3390/coatings10090821 - 25 Aug 2020

Cited by 4 | Viewed by 1986

Abstract

This article deals with the potential to reduce the amount of the residual stresses in the diamond films on cemented carbide inserts for improving their effective interfacial fatigue strength and thus their wear resistance. In this context, nano-crystalline diamond coatings (NCD) were deposited [...] Read more.

This article deals with the potential to reduce the amount of the residual stresses in the diamond films on cemented carbide inserts for improving their effective interfacial fatigue strength and thus their wear resistance. In this context, nano-crystalline diamond coatings (NCD) were deposited on cemented carbide inserts. A portion of these coated tools were annealed in vacuum for decreasing the amount of residual stresses in the film structure. The annealing temperature was appropriately selected for keeping the substrate strength properties invariable after the coating annealing. Inclined impact tests at ambient temperature on the untreated and heat-treated diamond coated tools were conducted for evaluating their effective interfacial fatigue strength. Depending upon the impact load, after a certain number of impacts, damages in the film-substrate interface develop, resulting in coating detachment and lifting. Via appropriate FEM (Finite Element Method)-evaluation of the impact imprints, the residual stresses in the diamond film structure were determined. Milling experiments were conducted for evaluating the cutting performance of the coated tools using aluminum foam as workpiece material. A correlation between the interfacial fatigue strength of diamond coatings and their residual stresses affected by annealings contributed to the explanation of the attained cutting results. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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11 pages, 3568 KiB

Open AccessArticle

The Analysis of Resistance to Brittle Cracking of Tungsten Doped TiB₂ Coatings Obtained by Magnetron Sputtering

by Jerzy Smolik, Joanna Kacprzyńska-Gołacka, Sylwia Sowa and Artur Piasek

Coatings 2020, 10(9), 807; https://doi.org/10.3390/coatings10090807 - 20 Aug 2020

Cited by 17 | Viewed by 2627

Abstract

In this work, the authors present the possibility of characterization of the fracture toughness in mode I (K_IC) for TiB₂ and TiB₂ coatings doped with different concentration of W (3%, 6% and 10%). The Young’s modulus, hardness and [...] Read more.

In this work, the authors present the possibility of characterization of the fracture toughness in mode I (K_IC) for TiB₂ and TiB₂ coatings doped with different concentration of W (3%, 6% and 10%). The Young’s modulus, hardness and fracture toughness of this coatings are extracted from nanoindentation experiments. The fracture toughness was evaluated using calculation of crack length measurement. An important observation is that increasing tungsten concentration in the range 0–10% changes the microstructure of the investigated coatings: from columnar structure for TiB₂ coating to nano-composite structure for Ti-B-W (10%) coating. It can be concluded that doping with concentration 10 at.% W causes an increase of the fracture toughness for the tested coatings. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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9 pages, 2137 KiB

Open AccessArticle

Polarization Controlled Dual Functional Reflective Planar Metalens in Near Infrared Regime

by Yuhui Zhang, Bowei Yang, Zhiying Liu and Yuegang Fu

Coatings 2020, 10(4), 389; https://doi.org/10.3390/coatings10040389 - 15 Apr 2020

Cited by 10 | Viewed by 2841

Abstract

The metalens has been a hotspot in scientific communications in recent years. The polarization-controlled functional metalens is appealing in metalens investigation. We propose a metalens with dual functions that are controlled by polarization states. In the first design, when applied with x- and [...] Read more.

The metalens has been a hotspot in scientific communications in recent years. The polarization-controlled functional metalens is appealing in metalens investigation. We propose a metalens with dual functions that are controlled by polarization states. In the first design, when applied with x- and y-polarized light, two focal spots with different focal lengths are acquired, respectively. The proposed metalens performs well when illuminated with adjacent wavelengths. In the second design, the reflected light is focused when applied with x-polarized light, and when applied with y-polarized light, the reflected light is split into two oblique paths. We believe that the results will provide a new method in light manipulation. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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12 pages, 1504 KiB

Open AccessArticle

Influences of Oxygen Ion Beam on the Properties of Magnesium Fluoride Thin Film Deposited Using Electron Beam Evaporation Deposition

by Gong Zhang, Xiuhua Fu, Shigeng Song, Kai Guo and Jing Zhang

Coatings 2019, 9(12), 834; https://doi.org/10.3390/coatings9120834 - 07 Dec 2019

Cited by 7 | Viewed by 3344

Abstract

Magnesium fluoride (MgF₂) materials are commonly used for near/medium infrared anti-reflection optical coatings due to their low refractive index and wide-range transparency. Ion assistant deposition is an important technique to increase the density of MgF₂ and reduce absorption around 2.94 [...] Read more.

Magnesium fluoride (MgF₂) materials are commonly used for near/medium infrared anti-reflection optical coatings due to their low refractive index and wide-range transparency. Ion assistant deposition is an important technique to increase the density of MgF₂ and reduce absorption around 2.94 µm caused by high porosity and moisture adsorption. However, the excessive energy of Argon ion will induce a color center and; therefore, lead to UV/Visible absorption. In this paper, oxygen ion was introduced to reduce the color center effect in MgF₂ thin film deposited using electron beam evaporation with ion assistant. The films were deposited on Bk7 and single crystal silicon substrates under various oxygen ion beam currents. The microstructure, optical constant, film density, stress, and adhesion are investigated, including the absorption properties at the infrared hydroxyl (–OH) vibration peak. The results show that as the oxygen ion beam current increases, the absorption value at the position of the infrared OH vibration, defects, and stress of the film decrease, while the refractive index increases. However, MgF₂ has poor adhesion using oxygen ion-assisted deposition. Thin MgF₂ film without ion beam assistant was used as adhesive layer, high density, and low absorption MgF₂ film with good adhesion was obtained. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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17 pages, 7773 KiB

Open AccessArticle

Combining Thermal Spraying and Magnetron Sputtering for the Development of Ni/Ni-20Cr Thin Film Thermocouples for Plastic Flat Film Extrusion Processes

by Wolfgang Tillmann, David Kokalj, Dominic Stangier, Volker Schöppner and Hatice Malatyali

Coatings 2019, 9(10), 603; https://doi.org/10.3390/coatings9100603 - 24 Sep 2019

Cited by 1 | Viewed by 2518

Abstract

In the digitalization of production, temperature determination is playing an increasingly important role. Thermal spraying and magnetron sputtering were combined for the development of Ni/Ni-20Cr thin film thermocouples for plastic flat film extrusion processes. On the thermally sprayed insulation layer, AlN and BCN [...] Read more.

In the digitalization of production, temperature determination is playing an increasingly important role. Thermal spraying and magnetron sputtering were combined for the development of Ni/Ni-20Cr thin film thermocouples for plastic flat film extrusion processes. On the thermally sprayed insulation layer, AlN and BCN thin films were deposited and analyzed regarding their structural properties and the interaction between the plastic melt and the surfaces using Ball-on-Disc experiments and High-Pressure Capillary Rheometer. A modular tool, containing the deposited Ni/Ni-20Cr thin film thermocouple, was developed and analyzed in a real flat film extrusion process. When calibrating the thin film thermocouple, an accurate temperature determination of the flowing melt was achieved. Industrial type K sensors were used as reference. In addition, PP foils were produced without affecting the surface quality by using thin film thermocouples. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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14 pages, 1272 KiB

Open AccessArticle

Simple Non-Destructive Method of Ultrathin Film Material Properties and Generated Internal Stress Determination Using Microcantilevers Immersed in Air

by Ivo Stachiv and Lifeng Gan

Coatings 2019, 9(8), 486; https://doi.org/10.3390/coatings9080486 - 01 Aug 2019

Cited by 6 | Viewed by 2963

Abstract

Recent progress in nanotechnology has enabled to design the advanced functional micro-/nanostructures utilizing the unique properties of ultrathin films. To ensure these structures can reach the expected functionality, it is necessary to know the density, generated internal stress and the material properties of [...] Read more.

Recent progress in nanotechnology has enabled to design the advanced functional micro-/nanostructures utilizing the unique properties of ultrathin films. To ensure these structures can reach the expected functionality, it is necessary to know the density, generated internal stress and the material properties of prepared films. Since these films have thicknesses of several tens of nm, their material properties, including density, significantly deviate from the known bulk values. As such, determination of ultrathin film material properties requires usage of highly sophisticated devices that are often expensive, difficult to operate, and time consuming. Here, we demonstrate the extraordinary capability of a microcantilever commonly used in a conventional atomic force microscope to simultaneously measure multiple material properties and internal stress of ultrathin films. This procedure is based on detecting changes in the static deflection, flexural and torsional resonant frequencies, and the corresponding quality factors of the microcantilever vibrating in air before and after film deposition. In contrast to a microcantilever in vacuum, where the quality factor depends on the combination of multiple different mechanical energy losses, in air the quality factor is dominated just by known air damping, which can be precisely controlled by changing the air pressure. Easily accessible expressions required to calculate the ultrathin film density, the Poisson’s ratio, and the Young’s and shear moduli from measured changes in the microcantilever resonant frequencies, and quality factors are derived. We also show that the impact of uncertainties on determined material properties is only minor. The validity and potential of the present procedure in material testing is demonstrated by (i) extracting the Young’s modulus of atomic-layer-deposited TiO₂ films coated on a SU-8 microcantilever from observed changes in frequency response and without requirement of knowing the film density, and (ii) comparing the shear modulus and density of Si₃N₄ films coated on the silicon microcantilever obtained numerically and by present method. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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9 pages, 4695 KiB

Open AccessArticle

Fabrication of a Conjugated Fluoropolymer Film Using One-Step iCVD Process and its Mechanical Durability

by Hyo Seong Lee, Hayeong Kim, Jeong Heon Lee and Jae B. Kwak

Coatings 2019, 9(7), 430; https://doi.org/10.3390/coatings9070430 - 08 Jul 2019

Cited by 17 | Viewed by 4442

Abstract

Most superhydrophobic surface fabrication techniques involve precise manufacturing process. We suggest initiated chemical vapor deposition (iCVD) as a novel CVD method to fabricate sufficiently durable superhydrophobic coating layers. The proposed method proceeds with the coating process at mild temperature (40 °C) with no [...] Read more.

Most superhydrophobic surface fabrication techniques involve precise manufacturing process. We suggest initiated chemical vapor deposition (iCVD) as a novel CVD method to fabricate sufficiently durable superhydrophobic coating layers. The proposed method proceeds with the coating process at mild temperature (40 °C) with no need of pretreatment of the substrate surface; the pressure and temperature are optimized as process parameters. To obtain a durable superhydrophobic film, two polymeric layers are conjugated in a sequential deposition process. Specifically, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (V4D4) monomer is introduced to form an organosilicon layer (pV4D4) followed by fluoropolymer formation by introducing 1H, 1H, 2H, 2H-Perfluorodecyl methacrylate (PFDMA). There is a high probability of covalent bond formation at the interface between the two layers. Accordingly, the mechanical durability of the conjugated fluoropolymer film (pV4D4-PFDMA) is reinforced because of cross-linking. The superhydrophobic coating on soft substrates, such as tissue paper and cotton fabric, was successfully demonstrated, and its durability was assessed against the mechanical stress such as tensile loading and abrasion. The results from both tests confirm the improvement of mechanical durability of the obtained film. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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10 pages, 4920 KiB

Open AccessArticle

Structure and Conductivity Studies of Scandia and Alumina Doped Zirconia Thin Films

by Mantas Sriubas, Nursultan Kainbayev, Darius Virbukas, Kristina Bočkutė, Živilė Rutkūnienė and Giedrius Laukaitis

Coatings 2019, 9(5), 317; https://doi.org/10.3390/coatings9050317 - 12 May 2019

Cited by 12 | Viewed by 3668

Abstract

In this work, scandia-doped zirconia (ScSZ) and scandia–alumina co-doped zirconia (ScSZAl) thin films were prepared by electron beam vapor deposition. X-ray diffraction (XRD) results indicated a presence of ZrO₂ cubic phase structure, yet Raman analysis revealed the existence of secondary tetragonal and [...] Read more.

In this work, scandia-doped zirconia (ScSZ) and scandia–alumina co-doped zirconia (ScSZAl) thin films were prepared by electron beam vapor deposition. X-ray diffraction (XRD) results indicated a presence of ZrO₂ cubic phase structure, yet Raman analysis revealed the existence of secondary tetragonal and rhombohedral phases. Thus, XRD measurements were supported by Raman spectroscopy in order to comprehensively analyze the structure of formed ScSZ and ScSZAl thin films. It was also found that Al dopant slows down the formation of the cubic phase. The impedance measurements affirmed the correlation of the amount of secondary phases with the conductivity results and nonlinear crystallite size dependence. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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8 pages, 2506 KiB

Open AccessArticle

Study on β-Ga₂O₃ Films Grown with Various VI/III Ratios by MOCVD

by Zeming Li, Teng Jiao, Daqiang Hu, Yuanjie Lv, Wancheng Li, Xin Dong, Yuantao Zhang, Zhihong Feng and Baolin Zhang

Coatings 2019, 9(5), 281; https://doi.org/10.3390/coatings9050281 - 26 Apr 2019

Cited by 13 | Viewed by 4228

Abstract

β-Ga₂O₃ films were grown on sapphire (0001) substrates with various O/Ga (VI/III) ratios by metal organic chemical vapor deposition. The effects of VI/III ratio on growth rate, structural, morphological, and Raman properties of the films were systematically studied. By varying [...] Read more.

β-Ga₂O₃ films were grown on sapphire (0001) substrates with various O/Ga (VI/III) ratios by metal organic chemical vapor deposition. The effects of VI/III ratio on growth rate, structural, morphological, and Raman properties of the films were systematically studied. By varying the VI/III ratio, the crystalline quality obviously changed. By decreasing the VI/III ratio from 66.9 × 10³ to 11.2 × 10³, the crystalline quality improved gradually, which was attributed to low nuclei density in the initial stage. However, crystalline quality degraded with further decrease of the VI/III ratio, which was attributed to excessive nucleation rate. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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20 pages, 8740 KiB

Open AccessArticle

Aluminum Coated Micro Glass Spheres to Increase the Infrared Reflectance

by Laura Schwinger, Sebastian Lehmann, Lukas Zielbauer, Benedikt Scharfe and Thorsten Gerdes

Coatings 2019, 9(3), 187; https://doi.org/10.3390/coatings9030187 - 12 Mar 2019

Cited by 7 | Viewed by 5794

Abstract

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The [...] Read more.

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The reflection behavior of the spheres can be further adapted by coating the surfaces of the spheres, e.g., by titanium dioxide or a metallic coating. Such coated spheres can be employed as, e.g., mid infrared (MIR)-reflective additives in wall paints to increase the thermal comfort in rooms. As a result, the demand of heating energy can be reduced. In this paper, the increase of the MIR-reflectance by applying an aluminum coating on MGS is discussed. Aluminum coatings are normally produced via the well-known Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). In our work, the Liquid Phase Deposition (LPD) method, as a new, non-vacuum method for aluminum coating on spherical spheres, is investigated as an alternative, scalable, and simple coating process. The LPD-coating is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and reflection measurements. The results are compared to a reference PVD-coating. It is shown that both sphere types, SMGS and MHGS, can be homogeneously coated with metallic aluminum using the LPD method but the surface morphology plays an important role concerning the reflection properties. With the SMGS, a smooth surface morphology and a reflectance increase to a value of 30% can be obtained. Due to a structured surface morphology, a reflection of only 5% could be achieved with the MHGS. However, post-treatments showed that a further increase is possible. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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13 pages, 3655 KiB

Open AccessArticle

In Situ Plasma Monitoring of PECVD nc-Si:H Films and the Influence of Dilution Ratio on Structural Evolution

by Yu-Lin Hsieh, Li-Han Kau, Hung-Jui Huang, Chien-Chieh Lee, Yiin-Kuen Fuh and Tomi T. Li

Coatings 2018, 8(7), 238; https://doi.org/10.3390/coatings8070238 - 06 Jul 2018

Cited by 15 | Viewed by 6862

Abstract

We report plasma-enhanced chemical vapor deposition (PECVD) hydrogenated nano-crystalline silicon (nc-Si:H) thin films. In particular, the effect of hydrogen dilution ratio (R = H₂/SiH₄) on structural and optical evolutions of the deposited nc-Si:H films were systematically investigated including [...] Read more.

We report plasma-enhanced chemical vapor deposition (PECVD) hydrogenated nano-crystalline silicon (nc-Si:H) thin films. In particular, the effect of hydrogen dilution ratio (R = H₂/SiH₄) on structural and optical evolutions of the deposited nc-Si:H films were systematically investigated including Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and low angle X-ray diffraction spectroscopy (XRD). Measurement results revealed that the nc-Si:H structural evolution, primarily the transition of nano-crystallization from the amorphous state to the nanocrystalline state, can be carefully induced by the adjustment of hydrogen dilution ratio (R). In addition, an in situ plasma diagnostic tool of optical emission spectroscopy (OES) was used to further characterize the crystallization rate index (H_α*/SiH*) that increases when hydrogen dilution ratio (R) rises, whereas the deposition rate decreases. Another in situ plasma diagnostic tool of quadruple mass spectrometry (QMS) also confirmed that the “optimal” range of hydrogen dilution ratio (R = 30–40) can yield nano-crystalline silicon (n-Si:H) growth due to the depletion of higher silane radicals. A good correlation between the plasma characteristics by in situ OES/QMS and the film characteristics by XRD, Raman and FTIR, for the transition of a-Si:H to nc-Si:H film from the hydrogen dilution ratio, was obtained. Full article

(This article belongs to the Special Issue Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation)

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