Research

15 pages, 3990 KiB

Open AccessArticle

TiO₂ Nanowires on TiO₂ Nanotubes Arrays (TNWs/TNAs) Decorated with Au Nanoparticles and Au Nanorods for Efficient Photoelectrochemical Water Splitting and Photocatalytic Degradation of Methylene Blue

by Ngo Ngoc Uyen, Le Thi Cam Tuyen, Le Trung Hieu, Thi Thu Tram Nguyen, Huynh Phuong Thao, Tho Chau Minh Vinh Do, Kien Trung Nguyen, Nguyen Thi Nhat Hang, Sheng-Rui Jian, Ly Anh Tu, Phuoc Huu Le and Chih-Wei Luo

Coatings 2022, 12(12), 1957; https://doi.org/10.3390/coatings12121957 - 13 Dec 2022

Cited by 3 | Viewed by 1789

Abstract

In this study, TiO₂ nanowires on TiO₂ nanotubes arrays (TNWs/TNAs) and Au-decorated TNWs/TNAs nanostructures are designed and fabricated as a new type of photoanode for photoelectrochemical (PEC) water splitting. The TNWs/TNAs were fabricated on Ti folds by anodization using an aqueous [...] Read more.

In this study, TiO₂ nanowires on TiO₂ nanotubes arrays (TNWs/TNAs) and Au-decorated TNWs/TNAs nanostructures are designed and fabricated as a new type of photoanode for photoelectrochemical (PEC) water splitting. The TNWs/TNAs were fabricated on Ti folds by anodization using an aqueous NH₄F/ethylene glycol solution, while Au nanoparticles (NPs) and Au nanorods (NRs) were synthesized by Turkevich methods. We studied the crystal structure, morphology, and PEC activity of four types of nanomaterial photoanodes, including TNWs/TNAs, Au NPs- TNWs/TNAs, Au NRs-TNWs/TNAs, and Au NPs-NRs-TNWs/TNAs. The TiO₂ and Au-TiO₂ samples exhibited pure anatase phase of TiO₂ with (0 0 4), (1 0 1), and (1 0 5) preferred orientations, while Au-TiO₂ presented a tiny XRD peak of Au (111) due to a small Au decorated content of 0.7 ± 0.2 at.%. In addition, the samples obtained a well-defined and uniformed structure of TNAs/TNWs; Au NPs (size of 19.0 ± 1.9 nm) and Au NRs (width of 14.8 ± 1.3 nm and length of 99.8 ± 15.1 nm) were primarily deposited on TNWs top layer; sharp Au/TiO₂ interfaces were observed from HRTEM images. The photocurrent density (J) of the photoanode nanomaterials was in the range of 0.24–0.4 mA/cm². Specifically, Au NPs-NRs- decorated TNWs/TNAs attained the highest J value of 0.4 mA/cm² because the decoration of Au NPs and Au NRs mixture onto TNWs/TNAs improved the light harvesting capability and the light absorption in the visible-infrared region, enhanced photogenerated carriers’ density, and increased electrons’ injection efficiency via the localized surface plasmon resonance (LSPR) effect occurring at the Au nanostructures. Furthermore, amongst the investigated nanophotocatalysts, the Au NPs-NRs TNWs/TNAs exhibited the highest photocatalytic activity in the degradation of methylene blue with a high reaction rate constant of 0.7 ± 0.07 h⁻¹, which was 2.5 times higher than that of the pristine TNWs/TNAs. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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14 pages, 11961 KiB

Open AccessArticle

Tunable Electrical Properties of Ti-B-N Thin Films Sputter-Deposited by the Reactive Gas Pulsing Process

by Charalampos Sakkas, Jean-Marc Cote, Joseph Gavoille, Jean-Yves Rauch, Pierre-Henri Cornuault, Anna Krystianiak, Olivier Heintz and Nicolas Martin

Coatings 2022, 12(11), 1711; https://doi.org/10.3390/coatings12111711 - 09 Nov 2022

Viewed by 1005

Abstract

Titanium-boron-nitrogen (Ti-B-N) thin films were deposited by RF reactive magnetron sputtering using a titanium diboride (TiB₂) target in an argon + nitrogen mixture. The argon mass flow rate was kept constant, whereas that of nitrogen was pulsed during the deposition. A [...] Read more.

Titanium-boron-nitrogen (Ti-B-N) thin films were deposited by RF reactive magnetron sputtering using a titanium diboride (TiB₂) target in an argon + nitrogen mixture. The argon mass flow rate was kept constant, whereas that of nitrogen was pulsed during the deposition. A constant pulsing period of P = 10 s was used, and the introduction time of the nitrogen gas (duty cycle (dc)) was systematically varied from dc = 0 to 100% of the pulsing period. This reactive gas pulsing process allowed the deposition of Ti-B-N thin films with various boron and nitrogen concentrations. Such adjustable concentrations in the films also led to changes in their electronic transport properties. Boron and nitrogen contents exhibited a reverse evolution as a function of the nitrogen duty cycle, which was correlated with the transition from a metallic to semiconducting-like behavior. A percolation model was applied to the electrical conductivity as a function of the nitrogen pulsing parameters, assuming some correlations with the evolution of the Ti-B-N thin film nanostructure. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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11 pages, 1591 KiB

Open AccessArticle

Design and Characterization of Nanostructured Titanium Monoxide Films Decorated with Polyaniline Species

by Tomas Sabirovas, Simonas Ramanavicius, Arnas Naujokaitis, Gediminas Niaura and Arunas Jagminas

Coatings 2022, 12(11), 1615; https://doi.org/10.3390/coatings12111615 - 24 Oct 2022

Viewed by 1068

Abstract

The fabrication of nanostructured composite materials is an active field of materials chemistry. However, the ensembles of nanostructured titanium monoxide and suboxide species decorated with polyaniline (PANI) species have not been deeply investigated up to now. In this study, such composites were formed [...] Read more.

The fabrication of nanostructured composite materials is an active field of materials chemistry. However, the ensembles of nanostructured titanium monoxide and suboxide species decorated with polyaniline (PANI) species have not been deeply investigated up to now. In this study, such composites were formed on both hydrothermally oxidized and anodized Ti substrates via oxidative polymerization of aniline. In this way, highly porous nanotube-shaped titanium dioxide (TiO₂) and nano leaflet-shaped titanium monoxide (TiO_x) species films loaded with electrically conductive PANI in an emeraldine salt form were designed. Apart from compositional and structural characterization with Field Emission Scanning Electron Microscopy (FESEM) and Raman techniques, the electrochemical properties were identified for each layer using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Based on the experimentally determined EIS parameters, it is envisaged that TiO-based nanomaterials decorated with PANI could find prospective applications in supercapacitors and biosensing. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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11 pages, 3786 KiB

Open AccessEditor’s ChoiceArticle

Finite Element Analysis of Nanoindentation Responses in Bi₂Se₃ Thin Films

by Shu-Wei Cheng, Bo-Syun Chen, Sheng-Rui Jian, Yu-Min Hu, Phuoc Huu Le, Le Thi Cam Tuyen, Jyh-Wei Lee and Jenh-Yih Juang

Coatings 2022, 12(10), 1554; https://doi.org/10.3390/coatings12101554 - 15 Oct 2022

Cited by 1 | Viewed by 1984

Abstract

In this study, the nanoindentation responses of Bi₂Se₃ thin film were quantitatively analyzed and simulated by using the finite element method (FEM). The hardness and Young’s modulus of Bi₂Se₃ thin films were experimentally determined using the continuous [...] Read more.

In this study, the nanoindentation responses of Bi₂Se₃ thin film were quantitatively analyzed and simulated by using the finite element method (FEM). The hardness and Young’s modulus of Bi₂Se₃ thin films were experimentally determined using the continuous contact stiffness measurements option built into a Berkovich nanoindenter. Concurrently, FEM was conducted to establish a model describing the contact mechanics at the film/substrate interface, which was then used to reproduce the nanoindentation load-depth and hardness-depth curves. As such, the appropriate material parameters were obtained by correlating the FEM results with the corresponding experimental load-displacement curves. Moreover, the detailed nanoindentation-induced stress distribution in the vicinity around the interface of Bi₂Se₃ thin film and c-plane sapphires was mapped by FEM simulation for three different indenters, namely, the Berkovich, spherical and flat punch indenters. The results indicated that the nanoindentation-induced stress distribution at the film/substrate interface is indeed strongly dependent on the indenter’s geometric shape. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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13 pages, 9549 KiB

Open AccessArticle

Bi Layer Properties in the Bi–FeNi GMR-Type Structures Probed by Spectroscopic Ellipsometry

by Natalia Kovaleva, Dagmar Chvostova, Ladislav Fekete and Alexandr Dejneka

Coatings 2022, 12(6), 872; https://doi.org/10.3390/coatings12060872 - 20 Jun 2022

Viewed by 1397

Abstract

Bismuth (Bi) having a large atomic number is characterized by a strong spin–orbit coupling (SOC) and is a parent compound of many 3D topological insulators (TIs). The ultrathin Bi films are supposed to be 2D TIs possessing a nontrivial topology, which opens the [...] Read more.

Bismuth (Bi) having a large atomic number is characterized by a strong spin–orbit coupling (SOC) and is a parent compound of many 3D topological insulators (TIs). The ultrathin Bi films are supposed to be 2D TIs possessing a nontrivial topology, which opens the possibility of developing new efficient technologies in the field of spintronics. Here we aimed at studying the dielectric function properties of ultrathin Bi/FeNi periodic structures using spectroscopic ellipsometry. The [Bi(d)–FeNi(1.8 nm)]

_{N}

GMR-type structures were grown by rf sputtering deposition on Sitall-glass (TiO

_{2}

) substrates. The ellipsometric angles

Ψ (ω)

and

Δ (ω)

were measured for the grown series (d = 0.6, 1.4, 2.0, and 2.5 nm, N = 16) of the multilayered film samples at room temperature for four angles of incidence of 60

^{\circ}

, 65

^{\circ}

, 70

^{\circ}

, and 75

^{\circ}

in a wide photon energy range of 0.5–6.5 eV. The measured ellipsometric angles,

Ψ (ω)

and

Δ (ω)

, were simulated in the framework of the corresponding multilayer model. The complex (pseudo)dielectric function spectra of the Bi layer were extracted. The GMR effects relevant for the studied Bi–FeNi MLF systems were estimated from the optical conductivity zero-limit (optical GMR effect). The obtained results demonstrated that the Bi layer possessed the surface metallic conductivity induced by the SOC effects, which was strongly enhanced on vanishing the semimetallic-like phase contribution on decreasing the layer thickness, indicating its nontrivial 2D topology properties. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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11 pages, 3088 KiB

Open AccessEditor’s ChoiceArticle

Effects of Substrate Temperature on Nanomechanical Properties of Pulsed Laser Deposited Bi₂Te₃ Films

by Hui-Ping Cheng, Phuoc Huu Le, Le Thi Cam Tuyen, Sheng-Rui Jian, Yu-Chen Chung, I-Ju Teng, Chih-Ming Lin and Jenh-Yih Juang

Coatings 2022, 12(6), 871; https://doi.org/10.3390/coatings12060871 - 20 Jun 2022

Cited by 4 | Viewed by 1855

Abstract

The correlations among microstructure, surface morphology, hardness, and elastic modulus of Bi₂Te₃ thin films deposited on c-plane sapphire substrates by pulsed laser deposition are investigated. X-ray diffraction (XRD) and transmission electron microscopy are used to characterize the microstructures of [...] Read more.

The correlations among microstructure, surface morphology, hardness, and elastic modulus of Bi₂Te₃ thin films deposited on c-plane sapphire substrates by pulsed laser deposition are investigated. X-ray diffraction (XRD) and transmission electron microscopy are used to characterize the microstructures of the Bi₂Te₃ thin films. The XRD analyses revealed that the Bi₂Te₃ thin films were highly (00l)-oriented and exhibited progressively improved crystallinity when the substrate temperature (T_S) increased. The hardness and elastic modulus of the Bi₂Te₃ thin films determined by nanoindentation operated with the continuous contact stiffness measurement (CSM) mode are both substantially larger than those reported for bulk samples, albeit both decrease monotonically with increasing crystallite size and follow the Hall—Petch relation closely. Moreover, the Berkovich nanoindentation-induced crack exhibited trans-granular cracking behaviors for all films investigated. The fracture toughness was significantly higher for films deposited at the lower T_S; meanwhile, the fracture energy was almost the same when the crystallite size was suppressed, which indicated a prominent role of grain boundary in governing the deformation characteristics of the present Bi₂Te₃ films. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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14 pages, 7710 KiB

Open AccessArticle

Fabrication of Carboxylated Carbon Nanotube Buckypaper Composite Films for Bovine Serum Albumin Detection

by Kuo-Jung Lee, Ming-Husan Lee, Yung-Hui Shih, Chao-Ping Wang, Hsun-Yu Lin and Sheng-Rui Jian

Coatings 2022, 12(6), 810; https://doi.org/10.3390/coatings12060810 - 10 Jun 2022

Cited by 1 | Viewed by 1299

Abstract

The salient point of this study is to fabricate carbon nanotube (CNT) buckypaper composite films prepared through the methods of pumping filtration and spin coating. Firstly, carboxylated CNTs were used to make the original buckypaper specimen and further modify the buckypaper surface by [...] Read more.

The salient point of this study is to fabricate carbon nanotube (CNT) buckypaper composite films prepared through the methods of pumping filtration and spin coating. Firstly, carboxylated CNTs were used to make the original buckypaper specimen and further modify the buckypaper surface by incorporating different surface modifiers. Then, all of original (unmodified) and modified buckypaper composite films had different concentrations of bovine serum albumin (BSA) added, and differential pulse voltammetry (DPV) electrochemical measurement was used to measure the characteristics of the various buckypaper composite films, after adding different concentrations of BSA. The experimental results show that the contact angles for four modified specimens are smaller than that of the original unmodified S–BP specimen (62°). These results indicate that the four modifiers used in this study can improve the hydrophilic properties of the original, unmodified S–BP specimen, and benefit the subsequent bonding of a modified specimen with aqueous BSA. In addition to the improvement of the hydrophilic properties of the modified specimen, which affects the bonding with BSA, the bonding type produced by the modifier also plays an essential role in the bonding between specimen and BSA. Therefore, the S–BP–EDC/NHS and S–BP–TA specimens have better linear dependence between log (BSA concentration) and oxidation current data. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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16 pages, 3195 KiB

Open AccessArticle

Synthesis and Electron-Beam Evaporation of Gadolinium-Doped Ceria Thin Films

by Fariza Kalyk, Artūras Žalga, Andrius Vasiliauskas, Tomas Tamulevičius, Sigitas Tamulevičius and Brigita Abakevičienė

Coatings 2022, 12(6), 747; https://doi.org/10.3390/coatings12060747 - 29 May 2022

Cited by 5 | Viewed by 2047

Abstract

Gadolinium-doped ceria (GDC) nanopowders, prepared using the co-precipitation synthesis method, were applied as a starting material to form ceria-based thin films using the electron-beam technique. The scanning electron microscopy (SEM )analysis of the pressed ceramic pellets’ cross-sectional views showed a dense structure with [...] Read more.

Gadolinium-doped ceria (GDC) nanopowders, prepared using the co-precipitation synthesis method, were applied as a starting material to form ceria-based thin films using the electron-beam technique. The scanning electron microscopy (SEM )analysis of the pressed ceramic pellets’ cross-sectional views showed a dense structure with no visible defects, pores, or cracks. The AC impedance spectroscopy showed an increase in the total ionic conductivity of the ceramic pellets with an increase in the concentration of Gd₂O₃ in GDC. The highest total ionic conductivity was obtained for Gd_0.1Ce_0.9O_2-δ (σ_total is 11 × 10⁻³ S∙cm⁻¹ at 600 °C), with activation energies of 0.85 and 0.67 eV in both the low- and high-temperature ranges, respectively. The results of the X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometer (ICP-OES) measurements revealed that the stoichiometry for the evaporated thin films differs, on average, by ~28% compared to the target material. The heat-treatment of the GDC thin films at 600 °C, 700 °C, 800 °C, and 900 °C for 1 h in the air had a minor effect on the surface roughness and the morphology. The results of Raman spectroscopy confirmed the improvement of the crystallinity for the corresponding thin films. The optimum heat-treating temperature for thin films does not exceed 800 °C. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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15 pages, 6502 KiB

Open AccessArticle

Van der Waals Epitaxial Growth of ZnO Films on Mica Substrates in Low-Temperature Aqueous Solution

by Hou-Guang Chen, Yung-Hui Shih, Huei-Sen Wang, Sheng-Rui Jian, Tzu-Yi Yang and Shu-Chien Chuang

Coatings 2022, 12(5), 706; https://doi.org/10.3390/coatings12050706 - 20 May 2022

Cited by 4 | Viewed by 2174

Abstract

In this article, we demonstrate the van der Waals (vdW) epitaxial growth of ZnO layers on mica substrates through a low-temperature hydrothermal process. The thermal pretreatment of mica substrates prior to the hydrothermal growth of ZnO is essential for growing ZnO crystals in [...] Read more.

In this article, we demonstrate the van der Waals (vdW) epitaxial growth of ZnO layers on mica substrates through a low-temperature hydrothermal process. The thermal pretreatment of mica substrates prior to the hydrothermal growth of ZnO is essential for growing ZnO crystals in epitaxy with the mica substrates. The addition of sodium citrate into the growth solution significantly promotes the growth of ZnO crystallites in a lateral direction to achieve fully coalesced, continuous ZnO epitaxial layers. As confirmed through transmission electron microscopy, the epitaxial paradigm of the ZnO layer on the mica substrate was regarded as an incommensurate van der Waals epitaxy. Furthermore, through the association of the Mist-CVD process, the high-density and uniform distribution of ZnO seeds preferentially occurred on mica substrates, leading to greatly improving the epitaxial qualities of the hydrothermally grown ZnO layers and obtaining flat surface morphologies. The electrical and optoelectrical properties of the vdW epitaxial ZnO layer grown on mica substrates were comparable with those grown on sapphire substrates through conventional solution-based epitaxy techniques. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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10 pages, 4772 KiB

Open AccessArticle

Effect of Substrate Temperature on the Properties of RF Magnetron Sputtered p-CuInO_x Thin Films for Transparent Heterojunction Devices

by Giji Skaria, Avra Kundu and Kalpathy B. Sundaram

Coatings 2022, 12(4), 500; https://doi.org/10.3390/coatings12040500 - 08 Apr 2022

Cited by 1 | Viewed by 1336

Abstract

Copper indium oxide (CuInO_x) thin films were deposited by the RF magnetron sputtering technique using a Cu₂O:In₂O₃ target at varying substrate temperatures up to 400 °C. Mutually exclusive requirements of having a p-type thin film along [...] Read more.

Copper indium oxide (CuInO_x) thin films were deposited by the RF magnetron sputtering technique using a Cu₂O:In₂O₃ target at varying substrate temperatures up to 400 °C. Mutually exclusive requirements of having a p-type thin film along with increased conductivity and high transparency were achieved by controlling the migration of indium oxide phases during the sputtering process, as verified by the XPS studies. A morphological study performed using SEM further confirmed the crystallization and the grain growth (95–135 nm) with increasing substrate temperatures, resulting in superior conductivity and an enhanced transparency of more than 70% in the 400–700 nm range. This is due to the controlled replacement of copper sites with indium while maintaining the p-type characteristic of the thin film. Optical studies carried out on the films indicated a bandgap change in the range of 2.46–2.99 eV as a function of substrate heating. A p-CuInO_x/n-Si heterojunction was fabricated with a measured knee voltage of 0.85 V. The photovoltaic behavior of the device was investigated and initial solar cell parameters are reported. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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13 pages, 3275 KiB

Open AccessFeature PaperArticle

Large Negative Photoresistivity in Amorphous NdNiO₃ Film

by Alexandr Stupakov, Tomas Kocourek, Natalia Nepomniashchaia, Marina Tyunina and Alexandr Dejneka

Coatings 2021, 11(11), 1411; https://doi.org/10.3390/coatings11111411 - 19 Nov 2021

Cited by 2 | Viewed by 1866

Abstract

A significant decrease in resistivity by 55% under blue lighting with ~0.4 J·mm⁻² energy density is demonstrated in amorphous film of metal-insulator NdNiO₃ at room temperature. This large negative photoresistivity contrasts with a small positive photoresistivity of 8% in epitaxial NdNiO [...] Read more.

A significant decrease in resistivity by 55% under blue lighting with ~0.4 J·mm⁻² energy density is demonstrated in amorphous film of metal-insulator NdNiO₃ at room temperature. This large negative photoresistivity contrasts with a small positive photoresistivity of 8% in epitaxial NdNiO₃ film under the same illumination conditions. The magnitude of the photoresistivity rises with the increasing power density or decreasing wavelength of light. By combining the analysis of the observed photoresistive effect with optical absorption and the resistivity of the films as a function of temperature, it is shown that photo-stimulated heating determines the photoresistivity in both types of films. Because amorphous films can be easily grown on a wide range of substrates, the demonstrated large photo(thermo)resistivity in such films is attractive for potential applications, e.g., thermal photodetectors and thermistors. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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14 pages, 3978 KiB

Open AccessFeature PaperArticle

Multiferroic and Nanomechanical Properties of Bi_1−xGd_xFeO₃ Polycrystalline Films (x = 0.00–0.15)

by Ting-Kai Lin, Huang-Wei Chang, Wan-Chi Chou, Chang-Ren Wang, Da-Hua Wei, Chi-Shun Tu and Pin-Yi Chen

Coatings 2021, 11(8), 900; https://doi.org/10.3390/coatings11080900 - 28 Jul 2021

Cited by 7 | Viewed by 1747

Abstract

In this work, we adopted pulsed laser deposition (PLD) with a Nd:YAG laser to develop Bi_1−xGd_xFeO₃ (BGFO) films on glass substrates. The phase composition, microstructure, ferroelectric, magnetic, and nanomechanical properties of BGFO films are studied. BGFO films [...] Read more.

In this work, we adopted pulsed laser deposition (PLD) with a Nd:YAG laser to develop Bi_1−xGd_xFeO₃ (BGFO) films on glass substrates. The phase composition, microstructure, ferroelectric, magnetic, and nanomechanical properties of BGFO films are studied. BGFO films with x = 0.00–0.15 were confirmed to mainly consist of the perovskite phase. The structure is transformed from rhombohedral for x = 0.00 to pseudo-cubic for x = 0.05–0.10, and an additional phase, orthorhombic, is coexisted for x = 0.15. With increasing Gd content, the microstructure and surface morphology analysis shows a gradual decrease in crystallite size and surface roughness. The hardness of 5.9–8.3 GPa, measured by nanoindentor, is mainly dominated by crystallized structure and grain size. Good ferroelectric properties are found for BGFO films with x = 0.00–0.15, where the largest remanent polarization (2P_r) of 133.5 µC/cm² is achieved for x = 0.10, related to low leakage and high BGFO(110) texture. The improved magnetic properties with the significant enhancement of saturation magnetization from 4.9 emu/cm³ for x = 0 to 23.9 emu/cm³ for x = 0.15 by Gd substitution is found and related to large magnetic moment of Gd³⁺ and suppressed spiral spin structure of G-type antiferromagnetism. Furthermore, we also discuss the mechanisms of leakage behavior as well as nanomechanical characterizations as a function of the Gd content. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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12 pages, 2023 KiB

Open AccessArticle

Optical and Structural Characterization of Cd-Free Buffer Layers Fabricated by Chemical Bath Deposition

by William Vallejo, Carlos Diaz-Uribe and Cesar Quiñones

Coatings 2021, 11(8), 897; https://doi.org/10.3390/coatings11080897 - 27 Jul 2021

Cited by 3 | Viewed by 1807

Abstract

Chemical bath deposition (CBD) is a suitable, inexpensive, and versatile synthesis technique to fabricate different semiconductors under soft conditions. In this study, we deposited Zn(O;OH)S thin films by the CBD method to analyze the effect of the number of thin film layers on [...] Read more.

Chemical bath deposition (CBD) is a suitable, inexpensive, and versatile synthesis technique to fabricate different semiconductors under soft conditions. In this study, we deposited Zn(O;OH)S thin films by the CBD method to analyze the effect of the number of thin film layers on structural and optical properties of buffer layers. Thin films were characterized by X-ray diffraction (XRD) and UV-Vis transmittance measurements. Furthermore, we simulated a species distribution diagram for Zn(O;OH)S film generation during the deposition process. The optical results showed that the number of layers determined the optical transmittance of buffer layers, and that the transmittance reduced from 90% (with one layer) to 50% (with four layers) at the visible range of the electromagnetic spectrum. The structural characterization indicated that the coatings were polycrystalline (α-ZnS and β-Zn(OH)₂ to four layers). Our results suggest that Zn(O;OH)S thin films could be used as buffer layers to replace CdS thin films as an optical window in thin-film solar cells. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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13 pages, 3224 KiB

Open AccessArticle

The Effect of RF Sputtering Temperature Conditions on the Structural and Physical Properties of Grown SbGaN Thin Film

by Cao Phuong Thao, Dong-Hau Kuo and Thi Tran Anh Tuan

Coatings 2021, 11(7), 752; https://doi.org/10.3390/coatings11070752 - 23 Jun 2021

Viewed by 1781

Abstract

By using a single ceramic SbGaN target containing a 14% Sb dopant, Sb_0.14GaN films were successfully grown on n-Si(100), SiO₂/Si(100), and quartz substrates by an RF reactive sputtering technology at different growth temperatures, ranging from 100 to 400 [...] Read more.

By using a single ceramic SbGaN target containing a 14% Sb dopant, Sb_0.14GaN films were successfully grown on n-Si(100), SiO₂/Si(100), and quartz substrates by an RF reactive sputtering technology at different growth temperatures, ranging from 100 to 400 °C. As a result, the structural characteristics, and optical and electrical properties of the deposited Sb_0.14GaN films were affected by the various substrate temperature conditions. By heating the temperature deposition differently, the sputtered Sb_0.14GaN films had a wurtzite crystal structure with a preferential (

10 \bar{1} 0

) plane, and these Sb_0.14GaN films experienced a structural distortion and exhibited p-type layers. At the highest depositing temperature of 400 °C, the Sb_0.14GaN film had the smallest bandgap energy of 2.78 eV, and the highest hole concentration of 8.97 × 10¹⁶ cm⁻³, a conductivity of 2.1 Scm⁻¹, and a high electrical mobility of 146 cm²V⁻¹s⁻¹. The p-Sb_0.14GaN/n-Si heterojunction diode was tested at different temperatures, ranging from 25 to 150 °C. The testing data showed that the change of testing temperature affected the electrical characteristics of the diode. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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13 pages, 2932 KiB

Open AccessArticle

Enhanced Methanol Oxidation Activity of PtRu/C_100−xMWCNTs_x (x = 0–100 wt.%) by Controlling the Composition of C-MWCNTs Support

by Dang Long Quan and Phuoc Huu Le

Coatings 2021, 11(5), 571; https://doi.org/10.3390/coatings11050571 - 14 May 2021

Cited by 9 | Viewed by 1934

Abstract

PtRu nanoparticles decorated on carbon-based supports are of great interest for direct methanol fuel cells (DMFCs). In this study, PtRu alloy nanoparticles decorated on carbon Vulcan XC-72 (C), multi-walled carbon nanotubes (MWCNTs), and C-MWCNTs composite supports were synthesized by co-reduction method. As a [...] Read more.

PtRu nanoparticles decorated on carbon-based supports are of great interest for direct methanol fuel cells (DMFCs). In this study, PtRu alloy nanoparticles decorated on carbon Vulcan XC-72 (C), multi-walled carbon nanotubes (MWCNTs), and C-MWCNTs composite supports were synthesized by co-reduction method. As a result, PtRu nanoparticles obtained a small mean size (d_mean = 1.8–3.8 nm) with a size distribution of 1–7 nm. We found that PtRu/C₆₀MWCNTs₄₀ possesses not only high methanol oxidation activity, but also excellent carbonaceous species tolerance ability, suggesting that C-MWCNTs composite support is better than either C or MWCNTs support. Furthermore, detailed investigation on PtRu/C_100−xMWCNTs_x (x = 10–50 wt.%) shows that the current density (J_f), catalyst tolerance ratio (J_f/J_r), and electron transfer resistance (R_et) are strongly affected by C-MWCNTs composition. The highest J_f is obtained for PtRu/C₇₀MWCNTs₃₀, which is considered as an optimal electrocatalyst. Meanwhile, both PtRu/C₇₀MWCNTs₃₀ and PtRu/C₆₀MWCNTs₄₀ exhibit a low R_et of 5.31–6.37 Ω·cm². It is found that C-MWCNTs composite support is better than either C or MWCNTs support in terms of simultaneously achieving the enhanced methanol oxidation activity and good carbonaceous species tolerance. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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10 pages, 4039 KiB

Open AccessFeature PaperArticle

Improving Transport Properties of GaN-Based HEMT on Si (111) by Controlling SiH₄ Flow Rate of the SiN_x Nano-Mask

by Jin-Ji Dai, Cheng-Wei Liu, Ssu-Kuan Wu, Sa-Hoang Huynh, Jhen-Gang Jiang, Sui-An Yen, Thi Thu Mai, Hua-Chiang Wen, Wu-Ching Chou, Chih-Wei Hu and Rong Xuan

Coatings 2021, 11(1), 16; https://doi.org/10.3390/coatings11010016 - 25 Dec 2020

Cited by 9 | Viewed by 3164

Abstract

The AlGaN/AlN/GaN high electron mobility transistor structures were grown on a Si (111) substrate by metalorganic chemical vapor deposition in combination with the insertion of a SiN_x nano-mask into the low-temperature GaN buffer layer. Herein, the impact of SiH₄ flow rate [...] Read more.

The AlGaN/AlN/GaN high electron mobility transistor structures were grown on a Si (111) substrate by metalorganic chemical vapor deposition in combination with the insertion of a SiN_x nano-mask into the low-temperature GaN buffer layer. Herein, the impact of SiH₄ flow rate on two-dimensional electron gas (2DEG) properties was comprehensively investigated, where an increase in SiH₄ flow rate resulted in a decrease in edge-type threading dislocation density during coalescence process and an improvement of 2DEG electronic properties. The study also reveals that controlling the SiH₄ flow rate of the SiN_x nano-mask grown at low temperatures in a short time is an effective strategy to overcome the surface desorption issue that causes surface roughness degradation. The highest electron mobility of 1970 cm²/V·s and sheet carrier concentration of 6.42 × 10¹² cm⁻² can be achieved via an optimized SiH₄ flow rate of 50 sccm. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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11 pages, 4151 KiB

Open AccessArticle

Improved Mechanical Properties and Corrosion Resistance of Mg-Based Bulk Metallic Glass Composite by Coating with Zr-Based Metallic Glass Thin Film

by Pei-Hua Tsai, Chung-I Lee, Sin-Mao Song, Yu-Chin Liao, Tsung-Hsiung Li, Jason Shian-Ching Jang and Jinn P. Chu

Coatings 2020, 10(12), 1212; https://doi.org/10.3390/coatings10121212 - 12 Dec 2020

Cited by 5 | Viewed by 2040

Abstract

Mg-based bulk metallic glass (BMG) and its composite (BMGC) can be excellent candidates as lightweight structure materials, but lack of anti-corrosion ability may restrict their application. In order to enhance the natural weak point of Mg-based BMGC, a 200-nm thick Zr-based metallic glass [...] Read more.

Mg-based bulk metallic glass (BMG) and its composite (BMGC) can be excellent candidates as lightweight structure materials, but lack of anti-corrosion ability may restrict their application. In order to enhance the natural weak point of Mg-based BMGC, a 200-nm thick Zr-based metallic glass thin film (MGTF) ((Zr₅₃Cu₃₀Ni₉Al₈)_99.5Si_0.5) was applied and its mechanical properties as well as its corrosion resistance were appraised. The results of a 3-point bending test revealed that the flexural strength of the Mg-based BMGC with 200-nm thick Zr-based MGTF coating can be greatly enhanced from 180 to 254 MPa. We propose that the Zr-based MGTF coating can help to cover any small defects of a substrate surface, provide a protecting layer to prevent stress concentration, and cease crack initiation from the specimen surface during bending tests. Moreover, the results of anti-corrosion behavior analysis revealed a similar trend between the Mg-based BMG, Mg-based BMGC, and Mg-based BMGC with Zr-based MGTF coating in 0.9 wt.% sodium chloride solution. The readings show a positive effect with the Zr-based MGTF coating. Therefore, the 200-nm thick Zr-based MGTF coating is a promising solution to provide protection for both mechanical and anti-corrosion behaviors of Mg-based BMGC and reinforce its capability as structure material in island environments. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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12 pages, 2337 KiB

Open AccessFeature PaperArticle

Effects of Stoichiometry on Structural, Morphological and Nanomechanical Properties of Bi₂Se₃ Thin Films Deposited on InP(111) Substrates by Pulsed Laser Deposition

by Yeong-Maw Hwang, Cheng-Tang Pan, Bo-Syun Chen, Phuoc Huu Le, Ngo Ngoc Uyen, Le Thi Cam Tuyen, Vanthan Nguyen, Chih-Wei Luo, Jenh-Yih Juang, Jihperng Leu and Sheng-Rui Jian

Coatings 2020, 10(10), 958; https://doi.org/10.3390/coatings10100958 - 05 Oct 2020

Cited by 8 | Viewed by 2517

Abstract

In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi₂Se₃ thin films prepared using a stoichiometric Bi₂Se₃ target and a Se-rich Bi₂Se₅ target are investigated. The Bi₂Se [...] Read more.

In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi₂Se₃ thin films prepared using a stoichiometric Bi₂Se₃ target and a Se-rich Bi₂Se₅ target are investigated. The Bi₂Se₃ films were grown on InP(111) substrates by using pulsed laser deposition. X-ray diffraction results revealed that all the as-grown thin films exhibited were highly c-axis-oriented Bi₂Se₃ phase with slight shift in diffraction angles, presumably due to slight stoichiometry changes. The energy dispersive X-ray spectroscopy analyses indicated that the Se-rich target gives rise to a nearly stoichiometric Bi₂Se₃ films, while the stoichiometric target only resulted in Se-deficient and Bi-rich films. Atomic force microscopy images showed that the films’ surfaces mainly consist of triangular pyramids with step-and-terrace structures with average roughness, R_a, being ~2.41 nm and ~1.65 nm for films grown with Bi₂Se₃ and Bi₂Se₅ targets, respectively. The hardness (Young’s modulus) of the Bi₂Se₃ thin films grown from the Bi₂Se₃ and Bi₂Se₅ targets were 5.4 GPa (110.2 GPa) and 10.3 GPa (186.5 GPa), respectively. The contact angle measurements of water droplets gave the results that the contact angle (surface energy) of the Bi₂Se₃ films obtained from the Bi₂Se₃ and Bi₂Se₅ targets were 80° (21.4 mJ/m²) and 110° (11.9 mJ/m²), respectively. Full article

(This article belongs to the Special Issue Recent Advances in the Growth and Characterizations of Thin Films)

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