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12 pages, 3184 KiB

Open AccessFeature PaperArticle

Melioration of Electrical and Optical Properties of Al and B Co-Doped ZnO Transparent Semiconductor Thin Films

by Chien-Yie Tsay and Shih-Hsun Yu

Coatings 2021, 11(10), 1259; https://doi.org/10.3390/coatings11101259 - 16 Oct 2021

Cited by 8 | Viewed by 2251

Abstract

Undoped, Al-doped and Al-B co-doped ZnO transparent semiconductor thin films were deposited on glass substrates by sol-gel method and spin coating technique. This study investigated the influence of Al (2 at.%) doping and Al (2 at.%)-B (1 or 2 at.%) co-doping on the [...] Read more.

Undoped, Al-doped and Al-B co-doped ZnO transparent semiconductor thin films were deposited on glass substrates by sol-gel method and spin coating technique. This study investigated the influence of Al (2 at.%) doping and Al (2 at.%)-B (1 or 2 at.%) co-doping on the microstructural, surface morphological, electrical and optical properties of the ZnO-based thin films. XRD analysis indicated that all as-prepared ZnO-based thin films were polycrystalline with a single-phase hexagonal wurtzite structure. The substitution of extrinsic dopants (Al or Al-B) into ZnO thin films can significantly degrade the crystallinity, refine the microstructures, improve surface flatness, enhance the optical transparency in the visible spectrum and lead to a shift in the absorption edge toward the short-wavelength direction. Experimental results showed that the Al-doped and Al-B co-doped ZnO thin films exhibited high average transmittance (>91.3%) and low average reflectance (<10%) in the visible region compared with the ZnO thin film. The optical parameters, including the optical bandgap, Urbach energy, extinction coefficient and refractive index, changed with the extrinsic doping level. Measured results of electrical properties revealed that the singly doped and co-doped samples exhibited higher electron concentrations and lower resistivities than those of the undoped sample and suggested that 2 at.% Al and 1 at.% B were the optimum dopant concentrations for achieving the best electrical properties in this study. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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12 pages, 10107 KiB

Open AccessArticle

The Determination of the Electronic Parameters of Thin Amorphous Organic Films by Ellipsometric and Spectrophotometric Study

by Natalia Nosidlak, Piotr Dulian, Dariusz Mierzwiński and Janusz Jaglarz

Coatings 2020, 10(10), 980; https://doi.org/10.3390/coatings10100980 - 14 Oct 2020

Cited by 4 | Viewed by 2161

Abstract

The aim of this work was the determination of the basic optical parameters and electronic structure of conjugated polymer films by two commonly used techniques—spectrophotometry and ellipsometry. Poly(3-hexylthiophene (P3HT) and poly(3-octylthiophene (P3OT) conductive polymers films deposited on a glass substrate by the spin-coating [...] Read more.

The aim of this work was the determination of the basic optical parameters and electronic structure of conjugated polymer films by two commonly used techniques—spectrophotometry and ellipsometry. Poly(3-hexylthiophene (P3HT) and poly(3-octylthiophene (P3OT) conductive polymers films deposited on a glass substrate by the spin-coating technique showed very comparable surface structures composed of grains of similar sizes and shapes. X-ray tests confirmed that the polythiophene layers are amorphous, which confirmed the correctness of the choice of the optical models used. Selected optical models (Lorentz, Tauc–Lorentz and Cody–Lorentz) have been applied in order to determine the thickness, and optical parameters such as refractive index and extinction coefficient, absolute absorption and electronic parameters (energy gap E_g, amplitude A and broadening B). Spectral absorption determined from spectrophotometric measurement is similar to the absorption spectrum obtained from the ellipsometry method with the application of oscillator models. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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16 pages, 7765 KiB

Open AccessArticle

Zirconium-Aluminum-Oxide Dielectric Layer with High Dielectric and Relatively Low Leakage Prepared by Spin-Coating and the Application in Thin-Film Transistor

by Zhihao Liang, Shangxiong Zhou, Wei Cai, Xiao Fu, Honglong Ning, Junlong Chen, Weijian Yuan, Zhennan Zhu, Rihui Yao and Junbiao Peng

Coatings 2020, 10(3), 282; https://doi.org/10.3390/coatings10030282 - 18 Mar 2020

Cited by 15 | Viewed by 4286

Abstract

In this paper, zirconium–aluminum–oxide (ZAO) dielectric layers were prepared by a solution method with intent to combine the high dielectric constant with a low leakage current density. As a result, dielectric layers with improved electrical properties as expected can be obtained by spin-coating [...] Read more.

In this paper, zirconium–aluminum–oxide (ZAO) dielectric layers were prepared by a solution method with intent to combine the high dielectric constant with a low leakage current density. As a result, dielectric layers with improved electrical properties as expected can be obtained by spin-coating the mixed precursor. The chemical and physical properties of the films were measured by thermogravimetric differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and a UV spectrometer. It is observed that the oxygen defects and the hydroxide in the films are reduced with the addition of high-bond-energy zirconia, while the films can remain large optical bond gaps thanks to the presence of alumina. The metal-insulator-metal (MIM) devices were fabricated, and it was seen that with a molar ratio of Zr:Al = 3:1 and an annealing temperature of 500 °C, the dielectric layer afforded the highest dielectric constant of 21.1, as well as a relatively low leakage current of 2.5 10⁻⁶ A/cm²@1MV/cm. Furthermore, the indium–gallium–zinc oxide thin-film transistors (IGZO-TFTs) with an optimal ZAO dielectric layer were prepared by the solution method and a mobility of 14.89 cm²/Vs, and a threshold voltage swing of 0.11 V/dec and a 6.1 10⁶on/off ratio were achieved at an annealing temperature of 500 °C. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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11 pages, 4121 KiB

Open AccessArticle

The Effect of Zirconium Doping on Solution-Processed Indium Oxide Thin Films Measured by a Novel Nondestructive Testing Method (Microwave Photoconductivity Decay)

by Jingying Zhang, Xiao Fu, Shangxiong Zhou, Honglong Ning, Yiping Wang, Dong Guo, Wei Cai, Zhihao Liang, Rihui Yao and Junbiao Peng

Coatings 2019, 9(7), 426; https://doi.org/10.3390/coatings9070426 - 05 Jul 2019

Cited by 8 | Viewed by 3450

Abstract

Solution-processed indium oxide is an ideal transparent semiconductor material with wide band gap. Zirconium is an element characterized by a strong binding ability to oxygen which can inhibit the formation of oxygen vacancies and reduce the surface defect state. In this paper, zirconium [...] Read more.

Solution-processed indium oxide is an ideal transparent semiconductor material with wide band gap. Zirconium is an element characterized by a strong binding ability to oxygen which can inhibit the formation of oxygen vacancies and reduce the surface defect state. In this paper, zirconium doped indium oxide (In_xZr_yO) thin films were prepared by the solution method, with indium oxide being doped with zirconium in order to tune the relative number of oxygen vacancies. The influence of the Zr doping concentration and the post-annealed temperature on the properties of the In_xZr_yO thin films was investigated. The results show that the doping process improves the crystallinity and relative density of the obtained films. A novel nondestructive method named microwave photoconductivity decay (μ-PCD) was used to evaluate the quality of In_xZr_yO thin films by simply measuring their response under laser irradiation. The relative number of oxygen vacancies and the minority carrier concentration achieved minimum values at 10 at.% Zr doping concentration. Furthermore, In_xZr_yO thin films with optimal properties from an electrical point of view were obtained at 10 at.% Zr doping concentration, annealed at 400 °C. Characterized by an average transmittance above 90% in the visible range, the obtained In_xZr_yO thin films can be used as active layer materials in the fabrication of high-performance thin film transistor (TFT) devices. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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13 pages, 2549 KiB

Open AccessArticle

Silicon Phthalocyanines as Acceptor Candidates in Mixed Solution/Evaporation Processed Planar Heterojunction Organic Photovoltaic Devices

by Marie D. M. Faure, Trevor M. Grant and Benoît H. Lessard

Coatings 2019, 9(3), 203; https://doi.org/10.3390/coatings9030203 - 21 Mar 2019

Cited by 15 | Viewed by 3657

Abstract

Silicon phthalocyanines (SiPc) are showing promise as both ternary additives and non-fullerene acceptors in organic photovoltaics (OPVs) as a result of their ease of synthesis, chemical stability and strong absorption. In this study, bis(3,4,5-trifluorophenoxy) silicon phthalocyanine ((345F)₂-SiPc)) and bis(2,4,6-trifluorophenoxy) silicon phthalocyanine [...] Read more.

Silicon phthalocyanines (SiPc) are showing promise as both ternary additives and non-fullerene acceptors in organic photovoltaics (OPVs) as a result of their ease of synthesis, chemical stability and strong absorption. In this study, bis(3,4,5-trifluorophenoxy) silicon phthalocyanine ((345F)₂-SiPc)) and bis(2,4,6-trifluorophenoxy) silicon phthalocyanine ((246F)₂-SiPc)) are employed as acceptors in mixed solution/evaporation planar heterojunction (PHJ) devices. The donor layer, either poly(3-hexylthiophene) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), was spin coated followed by the evaporation of the SiPc acceptor thin film. Several different donor/acceptor combinations were investigated in addition to investigations to determine the effect of film thickness on device performance. Finally, the effects of annealing, prior to SiPc deposition, after SiPc deposition, and during SiPc deposition were also investigated. The devices which performed the best were obtained using PCDTBT as the donor, with a 90 nm film of (345F)₂-SiPc as the acceptor, followed by thermal annealing at 150 °C for 30 min of the entire mixed solution/evaporation device. An open-circuit voltage (Voc) of 0.88 V and a fill factor (FF) of 0.52 were achieved leading to devices that outperformed corresponding fullerene-based PHJ devices. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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12 pages, 3812 KiB

Open AccessArticle

A Study on the Characteristics of Cu–Mn–Dy Alloy Resistive Thin Films

by Ho-Yun Lee, Chi-Wei He, Ying-Chieh Lee and Da-Chuan Wu

Coatings 2019, 9(2), 118; https://doi.org/10.3390/coatings9020118 - 13 Feb 2019

Cited by 4 | Viewed by 2886

Abstract

Cu–Mn–Dy resistive thin films were prepared on glass and Al₂O₃ substrates, which was achieved by co-sputtering the Cu–Mn alloy and dysprosium targets. The effects of the addition of dysprosium on the electrical properties and microstructures of annealed Cu–Mn alloy films [...] Read more.

Cu–Mn–Dy resistive thin films were prepared on glass and Al₂O₃ substrates, which was achieved by co-sputtering the Cu–Mn alloy and dysprosium targets. The effects of the addition of dysprosium on the electrical properties and microstructures of annealed Cu–Mn alloy films were investigated. The composition, microstructural and phase evolution of Cu–Mn–Dy films were characterized using field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. All Cu–Mn–Dy films showed an amorphous structure when the annealing temperature was set at 300 °C. After the annealing temperature was increased to 350 °C, the MnO and Cu phases had a significant presence in the Cu–Mn films. However, no MnO phases were observed in Cu–Mn–Dy films at 350 °C. Even Cu–Mn–Dy films annealed at 450 °C showed no MnO phases. This is because Dy addition can suppress MnO formation. Cu–Mn alloy films with 40% dysprosium addition that were annealed at 300 °C exhibited a higher resistivity of ~2100 μΩ·cm with a temperature coefficient of resistance of –85 ppm/°C. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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8 pages, 1911 KiB

Open AccessArticle

Effect of Oxygen Vacancy Ratio on a GaZTO Solar-Blind Photodetector

by Jhih-Chun Syu, Ming-Hung Hsu, Sheng-Po Chang, Shoou-Jinn Chang and Lucent Lu

Coatings 2018, 8(9), 293; https://doi.org/10.3390/coatings8090293 - 21 Aug 2018

Cited by 14 | Viewed by 3422

Abstract

A gallium-zinc-tin-oxide (GaZTO) solar-blind photodetector was fabricated via radio frequency sputtering. The transmittance of the GaZTO thin film was >80% in the visible light region, and its energy bandgap ranged from 4.11 to 4.23 eV. Manipulating the oxygen flows changed the ratio of [...] Read more.

A gallium-zinc-tin-oxide (GaZTO) solar-blind photodetector was fabricated via radio frequency sputtering. The transmittance of the GaZTO thin film was >80% in the visible light region, and its energy bandgap ranged from 4.11 to 4.23 eV. Manipulating the oxygen flows changed the ratio of oxygen vacancies, which was confirmed by X-ray photoelectron spectroscopy. The ratio of oxygen vacancies in the GaZTO thin films impacted the performance of the photodetectors. The photocurrent, responsivity, and ultraviolet–visible rejection ratio of the GaZTO solar-blind photodetector were 1.23 × 10⁻⁶ A, 9.12 × 10⁻² A/W, and 3.48 × 10⁴, respectively, at a 10 V bias under 280 nm light illumination. The transient responses of the synthesized photodetectors were measured and discussed. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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Review

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21 pages, 4565 KiB

Open AccessReview

Syntheses of Silver Nanowires Ink and Printable Flexible Transparent Conductive Film: A Review

by Xiaoli Wu, Zhimin Zhou, Yuehui Wang and Jingze Li

Coatings 2020, 10(9), 865; https://doi.org/10.3390/coatings10090865 - 07 Sep 2020

Cited by 30 | Viewed by 7785

Abstract

Nowadays, flexible transparent conductive film (FTCF) is one of the important components of many flexible electronic devices. Due to comprehensive performances on optoelectronics, FTCF based on silver nanowires (AgNWs) networks have received great attention and are expected to be a new generation of [...] Read more.

Nowadays, flexible transparent conductive film (FTCF) is one of the important components of many flexible electronic devices. Due to comprehensive performances on optoelectronics, FTCF based on silver nanowires (AgNWs) networks have received great attention and are expected to be a new generation of transparent conductive film materials. Due to its simple process, printed electronic technology is now an important technology for the rapid production of low-cost and high-quality flexible electronic devices. AgNWs-based FTCF fabricated by using printed electronic technology is considered to be the most promising process. Here, the preparation and performance of AgNW ink are introduced. The current printing technologies are described, including gravure printing, screen printing and inkjet printing. In addition, the latest methods to improve the conductivity, adhesion, and stability of AgNWs-based FTCF are introduced. Finally, the applications of AgNWs-based FTCF in solar cells, transparent film heaters, optoelectronic devices, touch panel, and sensors are introduced in detail. Therefore, combining various printing technologies with AgNWs ink may provide more opportunities for the development of flexible electronic devices in the future. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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27 pages, 3518 KiB

Open AccessFeature PaperReview

Transparent p-Type Semiconductors: Copper-Based Oxides and Oxychalcogenides

by Nengduo Zhang, Jian Sun and Hao Gong

Coatings 2019, 9(2), 137; https://doi.org/10.3390/coatings9020137 - 20 Feb 2019

Cited by 58 | Viewed by 8970

Abstract

While p-type transparent conducting materials (TCMs) are crucial for many optoelectronic applications, their performance is still not satisfactory. This has impeded the development of many devices such as photovoltaics, sensors, and transparent electronics. Among the various p-type TCMs proposed so far, Cu-based oxides [...] Read more.

While p-type transparent conducting materials (TCMs) are crucial for many optoelectronic applications, their performance is still not satisfactory. This has impeded the development of many devices such as photovoltaics, sensors, and transparent electronics. Among the various p-type TCMs proposed so far, Cu-based oxides and oxychalcogenides have demonstrated promising results in terms of their optical and electrical properties. Hence, they are the focus of this current review. Their basic material properties, including their crystal structures, conduction mechanisms, and electronic structures will be covered, as well as their device applications. Also, the development of performance enhancement strategies including doping/co-doping, annealing, and other innovative ways to improve conductivity will be discussed in detail. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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19 pages, 1917 KiB

Open AccessReview

The Use of Copper Oxide Thin Films in Gas-Sensing Applications

by Artur Rydosz

Coatings 2018, 8(12), 425; https://doi.org/10.3390/coatings8120425 - 26 Nov 2018

Cited by 102 | Viewed by 9672

Abstract

In this work, the latest achievements in the field of copper oxide thin film gas sensors are presented and discussed. Several methods and deposition techniques are shown with their advantages and disadvantages for commercial applications. Recently, CuO thin film gas sensors have been [...] Read more.

In this work, the latest achievements in the field of copper oxide thin film gas sensors are presented and discussed. Several methods and deposition techniques are shown with their advantages and disadvantages for commercial applications. Recently, CuO thin film gas sensors have been studied to detect various compounds, such as: nitrogen oxides, carbon oxides, hydrogen sulfide, ammonia, as well as several volatile organic compounds in many different applications, e.g., agriculture. The CuO thin film gas sensors exhibited high 3-S parameters (sensitivity, selectivity, and stability). Furthermore, the possibility to function at room temperature with long-term stability was proven as well, which makes this material very attractive in gas-sensing applications, including exhaled breath analysis. Full article

(This article belongs to the Special Issue Thin Films for Electronic Applications)

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