Editorial

5 pages, 6982 KiB

Open AccessEditorial

Editorial for the Special Issue on Advanced Thin-Films: Design, Fabrication and Applications

by Elena Kalinina

Micromachines 2024, 15(2), 255; https://doi.org/10.3390/mi15020255 - 09 Feb 2024

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The application scope of basic functional materials can be expanded through the creation of thin films due to the emergence of new unique properties of film materials that differ from their bulk analogues [...] Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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Research

Jump to: Editorial

12 pages, 4035 KiB

Open AccessArticle

Effect of Substrates on the Physicochemical Properties of Li₇La₃Zr₂O₁₂ Films Obtained by Electrophoretic Deposition

by Efim Lyalin, Evgeniya Il’ina, Alexander Pankratov, Tamara Kuznetsova and Elena Kalinina

Micromachines 2023, 14(12), 2153; https://doi.org/10.3390/mi14122153 - 25 Nov 2023

Viewed by 609

Abstract

Thin film technology of lithium-ion solid electrolytes should be developed for the creation of all-solid-state power sources. Solid electrolytes of the Li₇La₃Zr₂O₁₂ (LLZ) family are one of the promising membranes for all-solid-state batteries. LLZ films were [...] Read more.

Thin film technology of lithium-ion solid electrolytes should be developed for the creation of all-solid-state power sources. Solid electrolytes of the Li₇La₃Zr₂O₁₂ (LLZ) family are one of the promising membranes for all-solid-state batteries. LLZ films were obtained by electrophoretic deposition on Ti, Ni and steel substrates. The influence of different metal substrates on microstructure, phase composition and conductivity of the LLZ films after their heat treatment was studied. It was shown that the annealing of dried LLZ films in an Ar atmosphere leads to the transition from tetragonal modification to a low-temperature cubic structure. It was established that an impurity phase (Li₂CO₃) was not observed for LLZ films deposited on Ti foil after heat treatment, in contrast to films deposited on Ni and steel substrates. The highest lithium-ion conductivity values were achieved for the LLZ films annealed at 300 °C, 1.1 × 10⁻⁸ S cm⁻¹ (at 100 °C) and 1.0 × 10⁻⁶ S cm⁻¹ (at 200 °C). Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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9 pages, 1880 KiB

Open AccessArticle

Trench Formation under the Tunable Nanogap: Its Depth Depends on Maximum Strain and Periodicity

by Daehwan Park, Dukhyung Lee, Mahsa Haddadi Moghaddam and Dai-Sik Kim

Micromachines 2023, 14(11), 1991; https://doi.org/10.3390/mi14111991 - 27 Oct 2023

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Abstract

Metallic nanogaps have been studied for many years in the context of a significant amount of field enhancements. Nanogaps of macroscopic lengths for long-wave applications have attracted much interest, and recently one dimensional tunable nanogaps have been demonstrated using flexible PET substrates. For [...] Read more.

Metallic nanogaps have been studied for many years in the context of a significant amount of field enhancements. Nanogaps of macroscopic lengths for long-wave applications have attracted much interest, and recently one dimensional tunable nanogaps have been demonstrated using flexible PET substrates. For nanogaps on flexible substrates with applied tensile strain, large stress is expected in the vicinity of the gap, and it has been confirmed that several hundred nanometer-deep trenches form beneath the position of the nanogap because of this stress singularity. Here, we studied trench formation under nanogap structures using COMSOL Multiphysics 6.1. We constructed a 2D nanogap unit cell, consisting of gold film with a crack on a PDMS substrate containing a trench beneath the crack. Then, we calculated the von Mises stress at the bottom of the trench for various depths and spatial periods. Based on it, we derived the dependence of the trench depth on the strain and periodicity for various yield strengths. It was revealed that as the maximum tensile strain increases, the trench deepens and then diverges. Moreover, longer periods lead to larger depths for the given maximum strain and larger gap widths. These results could be applied to roughly estimate achievable gap widths and trench depths for stretchable zerogap devices. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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12 pages, 6035 KiB

Open AccessArticle

Preparation of MgO Self-Epitaxial Films for YBCO High-Temperature Coated Conductors

by Fei Yu, Yan Xue, Chaowei Zhong, Jiayi Song, Qiong Nie, Xin Hou and Baolei Wang

Micromachines 2023, 14(10), 1914; https://doi.org/10.3390/mi14101914 - 08 Oct 2023

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Abstract

Ion beam-assisted deposition (IBAD) has been proposed as a promising texturing technology that uses the film epitaxy method to obtain biaxial texture on a non-textured metal or compound substrate. Magnesium oxide (MgO) is the most well explored texturing material. In order to obtain [...] Read more.

Ion beam-assisted deposition (IBAD) has been proposed as a promising texturing technology that uses the film epitaxy method to obtain biaxial texture on a non-textured metal or compound substrate. Magnesium oxide (MgO) is the most well explored texturing material. In order to obtain the optimal biaxial texture, the actual thickness of the IBAD-MgO film must be controlled within 12nm. Due to the bombardment of ion beams, IBAD-MgO has large lattice deformation, poor texture, and many defects in the films. In this work, the solution deposition planarization (SDP) method was used to deposit oxide amorphous Y₂O₃ films on the surface of Hastelloy C276 tapes instead of the electrochemical polishing, sputtering-Al₂O₃ and sputtering-Y₂O₃ in the commercialized buffer layer. An additional homogeneous epitaxy MgO (epi-MgO) layer, which was used to improve the biaxial texture in the IBAD-MgO layer, was deposited on the IBAD-MgO layer by electron-beam evaporation. The effects of growth temperature, film thickness, deposition rate, and oxygen pressure on the texture and morphology of the epi-MgO film were systematically studied. The best full width at half maximum (FWHM) values were 2.2° for the out-of-plane texture and 4.8° for the in-plane texture for epi-MgO films, respectively. Subsequently, the LaMnO₃ cap layer and YBa₂Cu₃O₇-x (YBCO) functional layer were deposited on the epi-MgO layer to test the quality of the MgO layer. Finally, the critical current density of the YBCO films was 6 MA/cm² (77 K, 500 nm, self-field), indicating that this research provides a high-quality MgO substrate for the YBCO layer. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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14 pages, 5402 KiB

Open AccessArticle

High Oxygen Sensitivity of TiO₂ Thin Films Deposited by ALD

by Aleksei V. Almaev, Nikita N. Yakovlev, Dmitry A. Almaev, Maksim G. Verkholetov, Grigory A. Rudakov and Kristina I. Litvinova

Micromachines 2023, 14(10), 1875; https://doi.org/10.3390/mi14101875 - 29 Sep 2023

Cited by 1 | Viewed by 922

Abstract

The gas sensitivity and structural properties of TiO₂ thin films deposited by plasma-enhanced atomic layer deposition (ALD) were examined in detail. The TiO₂ thin films are deposited using Tetrakis(dimethylamido)titanium(IV) and oxygen plasma at 300 °C on SiO₂ substrates followed by [...] Read more.

The gas sensitivity and structural properties of TiO₂ thin films deposited by plasma-enhanced atomic layer deposition (ALD) were examined in detail. The TiO₂ thin films are deposited using Tetrakis(dimethylamido)titanium(IV) and oxygen plasma at 300 °C on SiO₂ substrates followed by annealing at temperatures of 800 °C. Gas sensitivity under exposure to O₂ within the temperature range from 30 °C to 700 °C was studied. The ALD-deposited TiO₂ thin films demonstrated high responses to O₂ in the dynamic range from 0.1 to 100 vol. % and low concentrations of H₂, NO₂. The ALD deposition allowed the enhancement of sensitivity of TiO₂ thin films to gases. The greatest response of TiO₂ thin films to O₂ was observed at a temperature of 500 °C and was 41.5 arb. un. under exposure to 10 vol. % of O₂. The responses of TiO₂ thin films to 0.1 vol. % of H₂ and 7 × 10^–4 vol. % of NO₂ at a temperature of 500 °C were 10.49 arb. un. and 10.79 arb. un., correspondingly. The resistance of the films increased due to the chemisorption of oxygen molecules on their surface that decreased the thickness of the conduction channel between the metal contacts. It was suggested that there are two types of adsorption centers on the TiO₂ thin films surface: oxygen is chemisorbed in the form of O^2– on the first one and O^– on the second one. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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24 pages, 10603 KiB

Open AccessArticle

Hierarchical Morphing Control of an Ultra-Lightweight Electro-Actuated Polymer Telescope with Thin-Film Actuators

by Kainan Wang, Yuxuan Gong, Yian Yu and André Preumont

Micromachines 2023, 14(10), 1855; https://doi.org/10.3390/mi14101855 - 28 Sep 2023

Viewed by 836

Abstract

This paper explores advanced shape control techniques for ultra-lightweight electro-actuated polymers with composite ferroelectric thin films. It begins with an overview of PVDF-TrFE film actuators used in the development of thin-shell composites, emphasizing the need to overcome constraints related to the electrode size [...] Read more.

This paper explores advanced shape control techniques for ultra-lightweight electro-actuated polymers with composite ferroelectric thin films. It begins with an overview of PVDF-TrFE film actuators used in the development of thin-shell composites, emphasizing the need to overcome constraints related to the electrode size for successful scalability. Strain generation in thin-film actuators is investigated, including conventional electrode-based methods and non-contact electron flux excitation. Numerical studies incorporate experimentally calibrated ferroelectric parameters, modeling non-contact actuation with an equivalent circuit representation. The potential distribution generated by electron flux injection highlights its potential for reducing print-through actuation issues. Additionally, the paper outlines a vision for the future of large thin-shell reflectors by integrating the discussed methods for charging ferroelectric polymer films. A hierarchical control strategy is proposed, combining macro- and micro-scale techniques to rectify shape errors in lightweight reflectors. These strategies offer the potential to enhance precision and performance in future spaceborne observation systems, benefiting space exploration and communication technologies. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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17 pages, 7648 KiB

Open AccessArticle

Synthesis, Structural, Optical, and Electrical Characterization of Biochitosan/Na_0.5Bi_0.5TiO₃ Composite Thin-Film Materials

by Jacem Zidani, Khaoula Hassine, Moneim Zannen, Andreas Zeinert, Antonio Da Costa, Anthony Ferri, Jamal Belhadi, Mustapha Majdoub, Mimoun El Marssi and Abdelilah Lahmar

Micromachines 2023, 14(10), 1841; https://doi.org/10.3390/mi14101841 - 27 Sep 2023

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Abstract

The purpose of this research work was to synthesis bioderived nanocomposite films by incorporating Na_0.5Bi_0.5TiO₃ (NBTO) nanoparticles into a chitosan matrix. The NBTO nanoparticles were synthesized using a traditional solid-state technique. Then, through a solution-casting approach, flexible composite [...] Read more.

The purpose of this research work was to synthesis bioderived nanocomposite films by incorporating Na_0.5Bi_0.5TiO₃ (NBTO) nanoparticles into a chitosan matrix. The NBTO nanoparticles were synthesized using a traditional solid-state technique. Then, through a solution-casting approach, flexible composite films were fabricated using chitosan polymer. The study presents a range of compelling findings. For structural and morphological insights, scanning electron microscopy (SEM) reveals a fascinating morphology where NBTO nanoparticles are uniformly dispersed and interlocked with other particles, forming interconnected grains with significant interspaces within the chitosan matrix. For the optical properties, the spectral response within the 300–800 nm range is primarily governed by light scattering attributed to NBTO particles with diameter sizes ranging from 100 to 400 nm, as well as the distinctive bandgap exhibited by the NBTO phase. The investigation of dielectric properties demonstrates that composite films exhibit markedly higher dielectric values in comparison to pure chitosan films. It is noteworthy that an increase in the NBTO content results in a corresponding increase in dielectric values, enhancing the versatility of these materials. Local piezoelectric measurements utilizing piezoresponse force microscopy confirm the expected piezoelectric and ferroelectric behavior of NBTO particles when dispersed within the chitosan matrix. This research introduces a novel class of biocompatible nanocomposite materials, combining impressive structural attributes, enhanced dielectric properties, and piezoelectric capabilities. The outcomes of this study hold substantial promise for advanced applications in opto- and piezoelectric technologies, marking a significant advancement in biologically sourced materials with multifunctional properties. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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15 pages, 3351 KiB

Open AccessArticle

Effect of Substrate Negative Bias on the Microstructural, Optical, Mechanical, and Laser Damage Resistance Properties of HfO₂ Thin Films Grown by DC Reactive Magnetron Sputtering

by Yingxue Xi, Xinghui Qin, Wantong Li, Xi Luo, Jin Zhang, Weiguo Liu and Pengfei Yang

Micromachines 2023, 14(9), 1800; https://doi.org/10.3390/mi14091800 - 21 Sep 2023

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Abstract

Hafnium oxide thin films have attracted great attention as promising materials for applications in the field of optical thin films and microelectronic devices. In this paper, hafnium oxide thin films were prepared via DC magnetron sputtering deposition on a quartz substrate. The influence [...] Read more.

Hafnium oxide thin films have attracted great attention as promising materials for applications in the field of optical thin films and microelectronic devices. In this paper, hafnium oxide thin films were prepared via DC magnetron sputtering deposition on a quartz substrate. The influence of various negative biases on the structure, morphology, and mechanical and optical properties of the obtained films were also evaluated. XRD results indicated that (

\bar{1} 11

)-oriented thin films with a monoclinic phase could be obtained under the non-bias applied conditions. Increasing the negative bias could refine the grain size and inhibit the grain preferred orientation of the thin films. Moreover, the surface quality and mechanical and optical properties of the films could be improved significantly along with the increase in the negative bias and then deteriorated as the negative bias voltage arrived at −50 V. It is evident that the negative bias is an effective modulation means to modify the microstructural, mechanical, and optical properties of the films. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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10 pages, 2073 KiB

Open AccessArticle

Electrodeposition and Properties of Composite Ni Coatings Modified with Multilayer Graphene Oxide

by Vitaly Tseluikin, Asel Dzhumieva, Andrey Yakovlev, Denis Tikhonov, Alena Tribis, Anastasia Strilets and Marina Lopukhova

Micromachines 2023, 14(9), 1747; https://doi.org/10.3390/mi14091747 - 07 Sep 2023

Cited by 1 | Viewed by 784

Abstract

Within the framework of this study, Ni-based composite electrochemical coatings (CECs) modified with multilayer graphene oxide (GO) processed using microwave radiation have been deposited. The process of these coatings’ electrodeposition in the potentiodynamic mode has been studied. The structure of Ni–GO and Ni–GO [...] Read more.

Within the framework of this study, Ni-based composite electrochemical coatings (CECs) modified with multilayer graphene oxide (GO) processed using microwave radiation have been deposited. The process of these coatings’ electrodeposition in the potentiodynamic mode has been studied. The structure of Ni–GO and Ni–GO (MW) CECs has been studied using X-ray phase analysis (XPA) and scanning electron microscopy (SEM).It has been shown that the addition of GO into a nickel deposit contributes to the formation of uniform fine-grained coatings. As a result, the microhardness of the Ni–GO (MW) CECs increases by 1.40 times compared to Ni without GO. The corrosion–electrochemical behavior of nickel CECs in 0.5 M H₂SO₄ solution was researched. It was established that the corrosion rate of the nickel–GO (MW) CEC in 3.5% NaCl decreases by about 1.70 times in contrast to unmodified nickel coatings. This effect is due to the absence of agglomeration of the graphene oxide in the volume of the nickel matrix and the impermeability of GO particles to the corrosive environment. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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10 pages, 2313 KiB

Open AccessArticle

Photodetection Properties of CdS/Si Heterojunction Prepared by Pulsed Laser Ablation in DMSO Solution for Optoelectronic Application

by Fatemah H. Alkallas, Shoug M. Alghamdi, Ameenah N. Al-Ahmadi, Amira Ben Gouider Trabelsi, Eman A. Mwafy, W. B. Elsharkawy, Emaan Alsubhe, Ayman M. Mostafa and Reham A. Rezk

Micromachines 2023, 14(8), 1546; https://doi.org/10.3390/mi14081546 - 31 Jul 2023

Cited by 2 | Viewed by 1155

Abstract

The high-quality n-type CdS on a p-type Si (111) photodetector device was prepared for the first time by a one-pot method based on an ns laser ablation method in a liquid medium. Cadmium target was ablated in DMSO solution, containing sulfur precursor, and [...] Read more.

The high-quality n-type CdS on a p-type Si (111) photodetector device was prepared for the first time by a one-pot method based on an ns laser ablation method in a liquid medium. Cadmium target was ablated in DMSO solution, containing sulfur precursor, and stirred, assisting in 1D-growth, to create the sulfide structure as CdS nano-ropes form, followed by depositing on the Si-substrate by spin coating. The morphological, structural, and optical characteristics of the CdS structure were examined using X-ray diffraction, transmission, and scanning electron microscopy, photoluminescence, and UV-VIS spectroscopy. From X-ray diffraction analysis, the growing CdS spheres have a good crystal nature, with a high purity and desired c-axis orientation along the (002) plane, and the crystallinity was around 30 nm. According to optical characterization, high transparency was found in the visible–near-infrared areas of the electromagnetic spectrum, and the CdS spheres have a direct optical energy band gap of 3.2 eV. After that, the CdS/Si hetero-structured device was found to be improved remarkably after adding CdS. It showed that the forward current is constantly linear, while the dark current is around 4.5 µA. Up to a bias voltage of 4 V, there was no breakdown, and the reverse current of the heterojunctions somewhat increased with reverse bias voltage, while the photocurrent reached up to 580 and 690 µA for using 15 and 30 W/cm² light power, respectively. Additionally, the ideal factors for CdS/Si heterojunction were 3.1 and 3.3 for 15 and 30 W/cm² light power, respectively. These results exhibited high performance compared to the same heterojunction produced by other techniques. In addition, this opens the route for obtaining more enhancements of these values based on the changing use of sulfide structures in the heterojunction formation. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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16 pages, 6956 KiB

Open AccessArticle

Effect of Plasma Excitation Power on the SiOxCyHz/TiOx Nanocomposite

by Tsegaye Gashaw Getnet, Nilson C. Cruz and Elidiane Cipriano Rangel

Micromachines 2023, 14(7), 1463; https://doi.org/10.3390/mi14071463 - 21 Jul 2023

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Abstract

Titanium dioxide has attracted a great deal of attention in the field of environmental purification due to its photocatalytic activity under ultraviolet light. Photocatalytic efficiency and the energy required to initiate the process remain the drawbacks that hinder the widespread adoption of the [...] Read more.

Titanium dioxide has attracted a great deal of attention in the field of environmental purification due to its photocatalytic activity under ultraviolet light. Photocatalytic efficiency and the energy required to initiate the process remain the drawbacks that hinder the widespread adoption of the process. Consistently with this, it is proposed here the polymerization of hexamethyldisiloxane fragments simultaneously to TiO₂ sputtering for the production of thin films in low-pressure plasma. The effect of plasma excitation power on the molecular structure and chemical composition of the films was evaluated by infrared spectroscopy. Wettability and surface energy were assessed by a sessile drop technique, using deionized water and diiodomethane. The morphology and elemental composition of the films were determined using scanning electron microscopy and energy dispersive spectroscopy, respectively. The thickness and roughness of the resulting films were measured using profilometry. Organosilicon-to-silica films, with different properties, were deposited by combining both deposition processes. Titanium was detected from the structures fabricated by the hybrid method. It has been observed that the proportion of titanium and particles incorporated into silicon-based matrices depends on the plasma excitation power. In general, a decrease in film thickness with increasing power has been observed. The presence of Ti in the plasma atmosphere alters the plasma deposition mechanism, affecting film deposition rate, roughness, and wettability. An interpretation of the excitation power dependence on the plasma activation level and sputtering yield is proposed. The methodology developed here will encourage researchers to create TiO₂ films on a range of substrates for their prospective use as sensor electrodes, water and air purification systems, and biocompatible materials. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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14 pages, 2220 KiB

Open AccessArticle

Comparative Analysis of Perovskite Solar Cells for Obtaining a Higher Efficiency Using a Numerical Approach

by Khaled Hussein Mahmoud, Abdullah Saad Alsubaie, Abdul Hakeem Anwer and Mohd Zahid Ansari

Micromachines 2023, 14(6), 1127; https://doi.org/10.3390/mi14061127 - 27 May 2023

Cited by 2 | Viewed by 1372

Abstract

Perovskite materials have gained considerable attention in recent years for their potential to improve the efficiency of solar cells. This study focuses on optimizing the efficiency of perovskite solar cells (PSCs) by investigating the thickness of the methylammonium-free absorber layer in the device [...] Read more.

Perovskite materials have gained considerable attention in recent years for their potential to improve the efficiency of solar cells. This study focuses on optimizing the efficiency of perovskite solar cells (PSCs) by investigating the thickness of the methylammonium-free absorber layer in the device structure. In the study we used a SCAPS-1D simulator to analyze the performance of MASnI₃ and CsPbI₃-based PSCs under AM1.5 illumination. The simulation involved using Spiro-OMeTAD as a hole transport layer (HTL) and ZnO as the electron transport layer (ETL) in the PSC structure. The results indicate that optimizing the thickness of the absorber layer can significantly increase the efficiency of PSCs. The precise bandgap values of the materials were set to 1.3 eV and 1.7 eV. In the study we also investigated the maximum thicknesses of the HTL, MASnI₃, CsPbI₃, and the ETL for the device structures, which were determined to be 100 nm, 600 nm, 800 nm, and 100 nm, respectively. The improvement techniques used in this study resulted in a high power-conversion efficiency (PCE) of 22.86% due to a higher value of V_OC for the CsPbI₃-based PSC structure. The findings of this study demonstrate the potential of perovskite materials as absorber layers in solar cells. It also provides insights into improving the efficiency of PSCs, which is crucial for advancing the development of cost-effective and efficient solar energy systems. Overall, this study provides valuable information for the future development of more efficient solar cell technologies. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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18 pages, 2666 KiB

Open AccessArticle

Photoelectrochemical Green Hydrogen Production Utilizing ZnO Nanostructured Photoelectrodes

by Sameerah I. Al-Saeedi

Micromachines 2023, 14(5), 1047; https://doi.org/10.3390/mi14051047 - 14 May 2023

Cited by 4 | Viewed by 1792

Abstract

One of the emerging and environmentally friendly technologies is the photoelectrochemical generation of green hydrogen; however, the cheap cost of production and the need for customizing photoelectrode properties are thought to be the main obstacles to the widespread adoption of this technology. The [...] Read more.

One of the emerging and environmentally friendly technologies is the photoelectrochemical generation of green hydrogen; however, the cheap cost of production and the need for customizing photoelectrode properties are thought to be the main obstacles to the widespread adoption of this technology. The primary players in hydrogen production by photoelectrochemical (PEC) water splitting, which is becoming more common on a worldwide basis, are solar renewable energy and widely available metal oxide based PEC electrodes. This study attempts to prepare nanoparticulate and nanorod-arrayed films to better understand how nanomorphology can impact structural, optical, and PEC hydrogen production efficiency, as well as electrode stability. Chemical bath deposition (CBD) and spray pyrolysis are used to create ZnO nanostructured photoelectrodes. Various characterization methods are used to investigate morphologies, structures, elemental analysis, and optical characteristics. The crystallite size of the wurtzite hexagonal nanorod arrayed film was 100.8 nm for the (002) orientation, while the crystallite size of nanoparticulate ZnO was 42.1 nm for the favored (101) orientation. The lowest dislocation values for (101) nanoparticulate orientation and (002) nanorod orientation are 5.6 × 10⁻⁴ and 1.0 × 10⁻⁴ dislocation/nm², respectively. By changing the surface morphology from nanoparticulate to hexagonal nanorod arrangement, the band gap is decreased to 2.99 eV. Under white and monochromatic light irradiation, the PEC generation of H₂ is investigated using the proposed photoelectrodes. The solar-to-hydrogen conversion rate of ZnO nanorod-arrayed electrodes was 3.72% and 3.12%, respectively, under 390 and 405 nm monochromatic light, which is higher than previously reported values for other ZnO nanostructures. The output H₂ generation rates for white light and 390 nm monochromatic illuminations were 28.43 and 26.11 mmol.h⁻¹cm⁻², respectively. The nanorod-arrayed photoelectrode retains 96.6% of its original photocurrent after 10 reusability cycles, compared to 87.4% for the nanoparticulate ZnO photoelectrode. The computation of conversion efficiencies, H₂ output rates, Tafel slope, and corrosion current, as well as the application of low-cost design methods for the photoelectrodes, show how the nanorod-arrayed morphology offers low-cost, high-quality PEC performance and durability. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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10 pages, 2385 KiB

Open AccessArticle

Structural Analysis of Mo Thin Films on Sapphire Substrates for Epitaxial Growth of AlN

by Jihong Kim, Youngil Kim and Sung-Min Hong

Micromachines 2023, 14(5), 966; https://doi.org/10.3390/mi14050966 - 28 Apr 2023

Viewed by 1218

Abstract

Aluminum nitride (AlN) thin film/molybdenum (Mo) electrode structures are typically required in microelectromechanical system applications. However, the growth of highly crystalline and c-axis-oriented AlN thin films on Mo electrodes remains challenging. In this study, we demonstrate the epitaxial growth of AlN thin [...] Read more.

Aluminum nitride (AlN) thin film/molybdenum (Mo) electrode structures are typically required in microelectromechanical system applications. However, the growth of highly crystalline and c-axis-oriented AlN thin films on Mo electrodes remains challenging. In this study, we demonstrate the epitaxial growth of AlN thin films on Mo electrode/sapphire (0001) substrates and examine the structural characteristics of Mo thin films to determine the reason contributing to the epitaxial growth of AlN thin films on Mo thin films formed on sapphire. Two differently oriented crystals are obtained from Mo thin films grown on sapphire substrates: (110)- and (111)-oriented crystals. The dominant (111)-oriented crystals are single-domain, and the recessive (110)-oriented crystals comprise three in-plane domains rotated by 120° with respect to each other. The highly ordered Mo thin films formed on sapphire substrates serve as templates for the epitaxial growth by transferring the crystallographic information of the sapphire substrates to the AlN thin films. Consequently, the out-of-plane and in-plane orientation relationships among the AlN thin films, Mo thin films, and sapphire substrates are successfully defined. Full article

(This article belongs to the Special Issue Advanced Thin-Films: Design, Fabrication and Applications)

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