Research

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17 pages, 12921 KiB

Open AccessArticle

Optimizing CuFeS₂ Chalcopyrite Thin Film Synthesis: A Comprehensive Three-Step Approach Using Ball-Milling, Thermal Evaporation, and Sulfurization Applied for Thermoelectric Generation

by Marcelo Augusto Malagutti, Ketan Lohani, Mirco D’Incau, Himanshu Nautiyal, Narges Ataollahi and Paolo Scardi

Appl. Sci. 2023, 13(18), 10172; https://doi.org/10.3390/app131810172 - 10 Sep 2023

Cited by 1 | Viewed by 1328

Abstract

CuFeS₂ (CFS) stands out as a promising narrow band-gap semiconductor for thermoelectric (TE) applications. However, its high lattice thermal conductivity is one of the factors hampering its potential for TE generation. A common strategy for tackling this problem is to produce this [...] Read more.

CuFeS₂ (CFS) stands out as a promising narrow band-gap semiconductor for thermoelectric (TE) applications. However, its high lattice thermal conductivity is one of the factors hampering its potential for TE generation. A common strategy for tackling this problem is to produce this material in thin film form. Thus, this study aims to practically understand and optimize the synthesis of CFS 2D materials using a simple three-step approach of ball-milling, thermal evaporation, and sulfurization of the CuFe metallic precursors. The tools for thin film characterization employ X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS), and Hall-effect measurements. DFT phase diagrams are also used to understand the energy of formation of the secondary phases present in the film. Here, we highlight that the ball-milling mechanisms, allied with high vacuum and high energy density during evaporation, are essential for the interdiffusion of Cu and Fe during the evaporation process. The film presented a flower-like morphology and p-type semiconducting behavior. A proof-of-concept Thermoelectric Generator (TEG) was designed in an in-plane geometry, showing a power output per unit active area of 114 nW cm⁻² (ΔT = 180 °C), comparable to other Cu-based materials, thus demonstrating the feasibility of this method of synthesis for TE applications. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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12 pages, 2764 KiB

Open AccessFeature PaperArticle

Study of Structure, Morphology and Optical Properties of Cobalt-Doped and Co/Al-co-Doped ZnO Thin Films Deposited by Electrospray Method

by Georgi Marinov, Biliana Georgieva, Marina Vasileva and Tsvetanka Babeva

Appl. Sci. 2023, 13(17), 9611; https://doi.org/10.3390/app13179611 - 25 Aug 2023

Cited by 1 | Viewed by 979

Abstract

A versatile electrospray method was utilized for deposition of thin ZnO films doped with Co (5%) (CZO) or co-doped with Co (2.5%) and Al (2.5%) (CAZO). Thin polycrystalline films with approximate thickness of 200 nm and high transmittance (more than 80%) were obtained. [...] Read more.

A versatile electrospray method was utilized for deposition of thin ZnO films doped with Co (5%) (CZO) or co-doped with Co (2.5%) and Al (2.5%) (CAZO). Thin polycrystalline films with approximate thickness of 200 nm and high transmittance (more than 80%) were obtained. No additional XRD peaks due to dopant impurities or dopant oxides were observed. The cobalt doping led to decrease in grain size and increase in crystallite size from 22 nm to 29 nm in the (101) direction. Smaller changes were observed for the CAZO films. Surface roughness of the films was measured using a 3D optical profiler. Surface roughness of the doped films was from 5 nm to 9 nm higher than that of the pure films. Refractive index, extinction coefficient and thickness of the films were calculated using ellipsometric measurements and were further used for determination of optical band gap and Urbach energy. Refractive index and optical band gap increased with doping from 1.86 and 3.29 eV for pure ZnO to 2.00 and 3.35 eV for CZO and 1.97 and 3.33 eV for CAZO films. Through calculation of Urbach energy (119 meV for pure ZnO, 236 meV for CZO and 138 meV for CAZO), it was demonstrated that doping leads to an increase in structural disorder, most pronounced in the case of Co doping. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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13 pages, 4507 KiB

Open AccessArticle

Surface Corrosion from Implant–Abutment Couplings with Different Connection Designs Influences Osteoblasts’ Function: A Novel Technique

by Ghada Alrabeah, Jonathan C. Knowles and Haralampos Petridis

Appl. Sci. 2023, 13(15), 8957; https://doi.org/10.3390/app13158957 - 04 Aug 2023

Viewed by 934

Abstract

The improved peri-implant bone response demonstrated when utilizing the platform-switching concept may result from the reduced levels of metal ions released from implant–abutment surfaces to the surrounding tissues. These corrosion products may play a major role in crestal bone remodeling around dental implants. [...] Read more.

The improved peri-implant bone response demonstrated when utilizing the platform-switching concept may result from the reduced levels of metal ions released from implant–abutment surfaces to the surrounding tissues. These corrosion products may play a major role in crestal bone remodeling around dental implants. This study evaluated the effect of different implant–abutment couplings (platform-matched vs. platform-switched) on osteoblasts’ function. Titanium alloy and cobalt–chrome alloy abutments were coupled with titanium cylinders, forming either platform-switched or platform-matched groups, and were incubated in human osteoblast cultures utilizing a novel direct-exposure technique. Viability was evaluated over 21 days using Alamar Blue assay. Apoptosis was measured after 24 h using flow cytometry. The expression of genes related to bone resorption was analysed over 21 days using a real-time quantitative polymerase chain reaction assay. Cell viability was reduced from day 4 to day 21 (p < 0.05), with higher rates of early apoptosis (p < 0.05) compared to the controls. Apoptosis was higher in the platform-matched groups (p < 0.05). The tested genes’ expression was up-regulated after 1 and 3 days of exposure to implant–abutment couplings (p < 0.05). The upregulation was more pronounced in platform-matched groups (p < 0.05). Exposure of osteoblasts to implant–abutment couplings induced adverse biological responses, which were more pronounced with platform-matched couplings. These reactions might be related to the increased amounts of metal ions released from the platform-matched couplings, highlighting the possible role of corrosion products in the mediation of crestal bone loss around dental implants. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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13 pages, 2594 KiB

Open AccessArticle

Influence of Al Doping on the Physical Properties of CuO Thin Films

by Radouane Daira, Bouzid Boudjema, Mohamed Bououdina, Mohamed Salah Aida and Catalin-Daniel Constantinescu

Appl. Sci. 2023, 13(14), 8193; https://doi.org/10.3390/app13148193 - 14 Jul 2023

Cited by 2 | Viewed by 1057

Abstract

The synthesis of cupric oxide (CuO) films on cost-efficient, optical grade borosilicate-crown glass substrates (BK7) via chemical spray pyrolysis (CSP), either in pure form or with a low concentration of Al doping (below 1%), is presented and discussed. As a non-toxic p-type [...] Read more.

The synthesis of cupric oxide (CuO) films on cost-efficient, optical grade borosilicate-crown glass substrates (BK7) via chemical spray pyrolysis (CSP), either in pure form or with a low concentration of Al doping (below 1%), is presented and discussed. As a non-toxic p-type semiconductor, exhibiting monoclinic crystal structure and widely tuneable band gap (Eg), it is used in various applications. The optical properties, morphology and crystalline phases of CuO films are influenced by substrate temperature during thin film growth (annealing) and also by chemical doping very often introduced to modify grain boundary energy. The importance of our research subject is therefore perfectly justified and is essentially based on the fact that the potential fields of application are wide. Thus, herein we emphasize impact of the annealing stage and Al doping upon the structural, optical and electrical properties of the resulting product. Raman spectroscopy analysis confirms the presence of vibrational bands characteristic of a CuO phase, while X-ray diffraction (XRD) confirms the polycrystalline nature of the pure films. The thickness of the CuO films grown at 350 °C over three annealing intervals is proportional to the annealing time, while the crystallite phase in the films is proportional with the annealing temperature. Furthermore, XRD analysis of the Al:CuO films indicates the formation of a monoclinic-type structure (CuO phase) exhibiting a preferred orientation along the (002) plane, together with a significant grain size reduction from ~88 to ~45 nm as Al content increases. The transmittance spectra (between 400 and 800 nm) reveal a decrease in the transmittance from 48% to 15% with as the Al doping ratio increases. Additionally, the bandgap energy of the films is measured, modelled and discussed, using data from an ultraviolet–visible (UV-Vis) spectrophotometer. The calculated Eg is approximately 3.5 eV, which decreases with respect to the increasing annealing temperature, while the electrical resistivity varies from ~19 to ~4.6 kOhm.cm. Finally, perspectives and applications of CuO films are suggested, since the films are found to have a remarkable improvement in their structure and optical properties when doped with Al. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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12 pages, 5074 KiB

Open AccessArticle

Electrochemical Analysis of MnO₂ (α, β, and γ)-Based Electrode for High-Performance Supercapacitor Application

by Raman Devi, Vinay Kumar, Sunil Kumar, Mamta Bulla, Shruti Sharma and Ashutosh Sharma

Appl. Sci. 2023, 13(13), 7907; https://doi.org/10.3390/app13137907 - 05 Jul 2023

Cited by 11 | Viewed by 2336

Abstract

MnO₂ is the most favorable material in power storage due to its technological significance and potential applications in pseudocapacitance (due to various oxidative states allowing efficient charge transfer to meet energy demands), where its properties are considerably influenced by its structure and [...] Read more.

MnO₂ is the most favorable material in power storage due to its technological significance and potential applications in pseudocapacitance (due to various oxidative states allowing efficient charge transfer to meet energy demands), where its properties are considerably influenced by its structure and surface morphology. In the present study, a facile hydrothermal route was used to produce different phases of MnO₂ (α, β, and γ) with different morphologies. The electrochemical performance of the synthesized phases was studied in aqueous sodium sulfate as an electrolyte. X-ray diffraction, UV–Vis spectroscopy, and Fourier-transform infrared spectroscopy were used to characterize the synthesized material. The surface morphology and topography were examined using field-emission scanning electron microscopy. The direct band gap of α-, β-, and γ-MnO₂ was found to be 1.86 eV, 1.08 eV, and 1.68 eV, lying in the semiconducting range, further enhancing the electrochemical performance. It was found that α-MnO₂ had a maximum specific capacitance of 138 F/g at 1 A/g, and the symmetric device fabricated using α-MnO₂ had a specific capacitance of 86 F/g at 1 A/g. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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9 pages, 1002 KiB

Open AccessCommunication

The Modification of Titanium Surface by Decomposition of Tannic Acid Coating

by Beata Kaczmarek-Szczepańska, Lidia Zasada, Marta Michalska-Sionkowska, Jithin Vishnu and Geetha Manivasagam

Appl. Sci. 2023, 13(8), 5204; https://doi.org/10.3390/app13085204 - 21 Apr 2023

Cited by 2 | Viewed by 1217

Abstract

Titanium is one of the most widely used metals in implantology owing to its reduced modulus, improved corrosion resistance and good biocompatibility. In spite of its excellent biocompatibility, it does not exhibit inherent antibacterial and antioxidant activity. Tannic acid is a naturally occurring [...] Read more.

Titanium is one of the most widely used metals in implantology owing to its reduced modulus, improved corrosion resistance and good biocompatibility. In spite of its excellent biocompatibility, it does not exhibit inherent antibacterial and antioxidant activity. Tannic acid is a naturally occurring polyphenol compound which exhibits excellent antibacterial, antioxidant and antimutagenic activity. The development of tannic acid-based coatings on the titanium surface holds great potential to reduce the risks associated with implant applications, thereby increasing the longevity of implants. In the present study, tannic acid was deposited on the titanium surface and the surface displayed a slightly improved hydrophilic character with an increase in surface energy. The release kinetics of tannic acid from titanium surface was analyzed and it showed an initial burst effect followed by a gradual decrease over time. Hemolysis tests revealed the erythrocyte compatibility of the developed surfaces. The improved hydrophilicity observed the release kinetics of tannic acid and reduced hemolysis rates revealed the potential of this facile technique for implant surface engineering applications. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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13 pages, 4440 KiB

Open AccessArticle

Structure Defects and Photovoltaic Properties of TiO₂:ZnO/CuO Solar Cells Prepared by Reactive DC Magnetron Sputtering

by Grzegorz Wisz, Paulina Sawicka-Chudy, Andrzej Wal, Maciej Sibiński, Piotr Potera, Rostyslaw Yavorskyi, Lyubomyr Nykyruy, Dariusz Płoch, Mariusz Bester, Marian Cholewa and Olena M. Chernikova

Appl. Sci. 2023, 13(6), 3613; https://doi.org/10.3390/app13063613 - 11 Mar 2023

Cited by 2 | Viewed by 1728

Abstract

The problem of copper diffusion in semiconductor devices has been known for several decades as copper has been used as an interconnecting (bonding) metal and has been intensively studied due to its high diffusion coefficient. The influence of the intensive diffusion of copper, [...] Read more.

The problem of copper diffusion in semiconductor devices has been known for several decades as copper has been used as an interconnecting (bonding) metal and has been intensively studied due to its high diffusion coefficient. The influence of the intensive diffusion of copper, depending on the technology of the deposition regimes, has been investigated in thin-film solar cells based on copper, zinc, and titanium oxides obtained by DC-reactive magnetron sputtering. The observed effect significantly changes the structure of the CuO films and affects the properties of the TiO₂:ZnO/CuO photocell. The composition of the layers and the copper diffusion in the photocells were studied using a cross-section obtained by scanning electron microscopy (SEM). The influence of the copper diffusion in the layers on the current–voltage (I-V) and power–voltage (P-V) characteristics and optical properties was investigated. The photoelectric behavior of two structures of thin-film solar cells was confirmed through -V research. The values of the open-circuit voltage (V_OC) and short-circuit current density (J_SC) of photovoltaic devices reached (11 ÷ 15) mV and (6.1 ÷ 6.8) μA, respectively. Furthermore, the Pmax, FF, RS, and RSH values were calculated and analyzed. The difference in the composition of the upper layer of the structure caused changes in the reflection spectra in the wavelength range of 190–2500 nm and, depending on the wavelength, varies in the range of 0–27%. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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15 pages, 2217 KiB

Open AccessArticle

Structure and Optical Properties of Transparent Cobalt-Doped ZnO Thin Layers

by Piotr Potera, Ihor S. Virt and Bogumił Cieniek

Appl. Sci. 2023, 13(4), 2701; https://doi.org/10.3390/app13042701 - 20 Feb 2023

Cited by 4 | Viewed by 1688

Abstract

Transparent thin layers of cobalt-doped ZnO were produced with the pulsed laser deposition method. The cobalt content of the original solid solution was 20% at. The crystallographic structure was examined by X-ray diffraction, which showed that the fabricated layers crystallized in the wurtzite [...] Read more.

Transparent thin layers of cobalt-doped ZnO were produced with the pulsed laser deposition method. The cobalt content of the original solid solution was 20% at. The crystallographic structure was examined by X-ray diffraction, which showed that the fabricated layers crystallized in the wurtzite phase and had a dominant orientation along the a-axis. The texture coefficient (increasing from F = 0.08 for the non-annealed layer to F = 0.94 for the annealed layer at 400 °C) and grain size (D = 110 ÷ 140 nm) were calculated. Optical constants, such as the refractive index n (1.62) and the extinction coefficient k (0.1 ÷ 0.4), were determined from the ultraviolet–visible–near-infrared transmission spectrum using the envelope method. The value of the optical band gap was determined, which is lower than for pure ZnO. Increasing the annealing temperature of the ZnO:Co layer increases the Urbach energy from 0.20 to 0.25 eV, which shows the difference in the type of growth defects in the ZnO matrix. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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14 pages, 31273 KiB

Open AccessArticle

Evaluation of the Structural, Optical and Photoconversion Efficiency of ZnO Thin Films Prepared Using Aerosol Deposition

by May Zin Toe, Wai Kian Tan, Hiroyuki Muto, Go Kawamura, Atsunori Matsuda and Swee-Yong Pung

Appl. Sci. 2023, 13(3), 1905; https://doi.org/10.3390/app13031905 - 01 Feb 2023

Viewed by 1475

Abstract

As compared to other deposition techniques such as atomic layer deposition, chemical vapour deposition and sputtering, aerosol deposition (AD) is a simple and cost-effective technique to produce ZnO thin films. In this work, the effect of deposition cycles on the structural, optical, and [...] Read more.

As compared to other deposition techniques such as atomic layer deposition, chemical vapour deposition and sputtering, aerosol deposition (AD) is a simple and cost-effective technique to produce ZnO thin films. In this work, the effect of deposition cycles on the structural, optical, and photo-conversion efficiency (PCE) of dye sensitized solar cells of ZnO thin films deposited by AD (AZ) was systematically studied. The structural, optical, and PCE% of two-cycle deposited ZnO thin film (AZ-II) exhibited the highest performance. Further increment in deposition cycle caused deterioration in the structural, optical, and PCE performance. The thickness of ZnO thin films decreased due to abrasion of the deposited film by the subsequent stream of highly energetic ZnO particles. Loosely bound particles could be found on the surface of ZnO thin film after three deposition cycles (AZ-III). The AZ-III films exhibited poor crystal quality, with many crystal defects such as interstitial oxygen as suggested in room temperature photoluminescence analysis. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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13 pages, 4806 KiB

Open AccessArticle

Influence of Annealing on Gas-Sensing Properties of TiOx Coatings Prepared by Gas Impulse Magnetron Sputtering with Various O₂ Content

by Damian Wojcieszak, Paulina Kapuścik and Wojciech Kijaszek

Appl. Sci. 2023, 13(3), 1724; https://doi.org/10.3390/app13031724 - 29 Jan 2023

Cited by 2 | Viewed by 1066

Abstract

TiOx films were prepared by gas impulse magnetron sputtering under oxygen-deficient (ODC) and oxygen-rich conditions (ORC) and annealing at 100–800 °C was used. The O₂ content had an effect on their transparency level (T_λ). The films from the ORC mode [...] Read more.

TiOx films were prepared by gas impulse magnetron sputtering under oxygen-deficient (ODC) and oxygen-rich conditions (ORC) and annealing at 100–800 °C was used. The O₂ content had an effect on their transparency level (T_λ). The films from the ORC mode had ca. T_λ = 60%, which decreased slightly in the VIS range after annealing. The film from the ODC mode had lower transmission (ca. <10%), which increased in the NIR range after annealing by up to ca. 60%. Differences in optical band gap (E_g^opt) and Urbach energy (E_u) were also observed. The deposition parameters had an influence on the microstructure of TiOx coatings. The ORC and ODC modes resulted in columnar and grainy structures, respectively. Directly after deposition, both coatings were amorphous according to the GIXRD results. In the case of TiOx^ORC films, this state was retained even after annealing, while for TiOx^ODC, the crystalline forms of Ti and TiO₂-anatase were revealed with increasing temperature. Sensor studies have shown that the response to H₂ in the coating deposited under oxygen-rich conditions was characteristic of n-type conductivity, while oxygen-deficient conditions led to a p-type response. The highest sensor responses were achieved for TiOx^ODC annealed at 300 °C and 400 °C. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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Review

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20 pages, 1761 KiB

Open AccessReview

Bioactive Glasses for Soft and Hard Tissue Healing Applications—A Short Review

by Irina Negut and Carmen Ristoscu

Appl. Sci. 2023, 13(10), 6151; https://doi.org/10.3390/app13106151 - 17 May 2023

Cited by 10 | Viewed by 2448

Abstract

Bioactive glasses have developed into a variety of items that are used in order to treat a wide range of medical problems. Apart from being mostly applied in the healing processes of hard tissues, bioactive glasses are becoming very popular materials in soft [...] Read more.

Bioactive glasses have developed into a variety of items that are used in order to treat a wide range of medical problems. Apart from being mostly applied in the healing processes of hard tissues, bioactive glasses are becoming very popular materials in soft tissues healing. Bioactive glasses have exhibited the ability to accelerate skin regeneration by enhancing angiogenesis and collagen deposition in the proliferation stage, as well as positive effects on all the other important stages of wound healing. They can adhere to hard tissues such as bone and aid in the regeneration of those tissues by forming a calcium–phosphate-like layer on their surfaces. The formation of this apatite layer results in a linkage between the hard tissue and the glass, which further leads to bone healing. This short review summarizes the dynamic process of wound healing along with the basic concepts of bioactive glasses applied in this domain. We aimed to explore constructs which aid different phases of wound healing. Moreover, several research studies dedicated to bioactive glass thin films are briefly discussed. Full article

(This article belongs to the Special Issue Advances in Surface Science and Thin Films)

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