Research

13 pages, 20437 KiB

Open AccessArticle

Bias Stability Enhancement in Thin-Film Transistor with a Solution-Processed ZrO₂ Dielectric as Gate Insulator

by Shangxiong Zhou, Zhiqiang Fang, Honglong Ning, Wei Cai, Zhennan Zhu, Jinglin Wei, Xubing Lu, Weijian Yuan, Rihui Yao and Junbiao Peng

Appl. Sci. 2018, 8(5), 806; https://0-doi-org.brum.beds.ac.uk/10.3390/app8050806 - 17 May 2018

Cited by 10 | Viewed by 4953

Abstract

In this paper, a high-k metal-oxide film (ZrO₂) was successfully prepared by a solution-phase method, and whose physical properties were measured by X-ray diffraction (XRD), X-ray reflectivity (XRR) and atomic force microscopy (AFM). Furthermore, indium–gallium–zinc oxide thin-film transistors (IGZO-TFTs) with high-k [...] Read more.

In this paper, a high-k metal-oxide film (ZrO₂) was successfully prepared by a solution-phase method, and whose physical properties were measured by X-ray diffraction (XRD), X-ray reflectivity (XRR) and atomic force microscopy (AFM). Furthermore, indium–gallium–zinc oxide thin-film transistors (IGZO-TFTs) with high-k ZrO₂ dielectric layers were demonstrated, and the electrical performance and bias stability were investigated in detail. By spin-coating 0.3 M precursor six times, a dense ZrO₂ film, with smoother surface and fewer defects, was fabricated. The TFT devices with optimal ZrO₂ dielectric exhibit a saturation mobility up to 12.7 cm² V⁻¹ s⁻¹, and an on/off ratio as high as 7.6 × 10⁵. The offset of the threshold voltage was less than 0.6 V under positive and negative bias stress for 3600 s. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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10 pages, 2223 KiB

Open AccessArticle

Temperature-Dependent Electrical Properties of Al₂O₃-Passivated Multilayer MoS₂ Thin-Film Transistors

by Seok Hwan Jeong, Na Liu, Heekyeong Park, Young Ki Hong and Sunkook Kim

Appl. Sci. 2018, 8(3), 424; https://0-doi-org.brum.beds.ac.uk/10.3390/app8030424 - 12 Mar 2018

Cited by 19 | Viewed by 7646

Abstract

It is becoming more important for electronic devices to operate stably and reproducibly under harsh environments, such as extremely low and/or high temperatures, for robust and practical applications. Here, we report on the effects of atomic-layer-deposited (ALD) aluminum oxide (Al₂O₃ [...] Read more.

It is becoming more important for electronic devices to operate stably and reproducibly under harsh environments, such as extremely low and/or high temperatures, for robust and practical applications. Here, we report on the effects of atomic-layer-deposited (ALD) aluminum oxide (Al₂O₃) passivation on multilayer molybdenum disulfide (MoS₂) thin-film transistors (TFTs) and their temperature-dependent electrical properties, especially at a high temperature range from 293 K to 380 K. With the aid of ultraviolet-ozone treatment, an Al₂O₃ layer was uniformly applied to cover the entire surface of MoS₂ TFTs. Our Al₂O₃-passivated MoS₂ TFTs exhibited not only a dramatic reduction of hysteresis but also enhancement of current in output characteristics. In addition, we investigated the temperature-dependent behaviors of the TFT performance, including intrinsic carrier mobility based on the Y-function method. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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28566 KiB

Open AccessArticle

Printing Speed and Quality Enhancement by Controlling the Surface Energy of Cliché in Reverse Offset Printing

by Young Tae Cho, Yeonho Jeong, Youn Jae Kim, Sin Kwon, Seung-Hyun Lee, Kwang Young Kim, Dongwoo Kang and Taik-Min Lee

Appl. Sci. 2017, 7(12), 1302; https://0-doi-org.brum.beds.ac.uk/10.3390/app7121302 - 15 Dec 2017

Cited by 10 | Viewed by 6304

Abstract

Printed electronics is one of the emerging technologies owing to its low cost and productivity. Recently, many researchers tried to adapt printing technology to the fabrication of fine electronic patterns on flexible substrates, including the gate line of thin film transistors. In this [...] Read more.

Printed electronics is one of the emerging technologies owing to its low cost and productivity. Recently, many researchers tried to adapt printing technology to the fabrication of fine electronic patterns on flexible substrates, including the gate line of thin film transistors. In this study, we fabricated a flexible cliché using the nanoimprint process and used it in reverse offset printing. Then, we analyzed the effect of the surface energy of the imprinted cliché on process parameters, such as printing speed and rolling direction. We showed that the productivity of the process and quality of printed pattern can be considerably enhanced by controlling the surface energy of the cliché. When a flexible cliché is manufactured using a resin with a surface energy considerably different from that of the blanket, the ink can be detached easily and fine patterns can be engraved successfully regardless of the pattern shape. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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4383 KiB

Open AccessArticle

Could We Realize the Fully Flexible System by Real-Time Computing with Thin-Film Transistors?

by Qin Li, Zheyu Liu, Fei Qiao, Qi Wei and Huazhong Yang

Appl. Sci. 2017, 7(12), 1224; https://0-doi-org.brum.beds.ac.uk/10.3390/app7121224 - 27 Nov 2017

Cited by 2 | Viewed by 3876

Abstract

Flexible electronic devices, such as the typical thin-film transistors, are widely adopted in the area of sensors, displayers, wearable equipment, and such large-area applications, for their features of bending and stretching; additionally, in some applications of lower-resolution data converters recently, where a trend [...] Read more.

Flexible electronic devices, such as the typical thin-film transistors, are widely adopted in the area of sensors, displayers, wearable equipment, and such large-area applications, for their features of bending and stretching; additionally, in some applications of lower-resolution data converters recently, where a trend appears that implementing more parts of system with flexible devices to realize the fully flexible system. Nevertheless, relatively fewer works on the computation parts with flexible electronic devices are reported, due to their poor carrier mobility, which blocks the way to realize the fully flexible systems with uniform manufacturing process. In this paper, a novel circuit architecture for image processing accelerator using Oxide Thin-film transistor (TFT), which could realize real-time image pre-processing and classification in the analog domain, is proposed, where the performance and fault-tolerance of image signal processing is exploited. All of the computation is done in the analog signal domain and no clock signal is needed. Therefore, certain weaknesses of flexible electronic devices, such as low carrier mobility, could be remedied dramatically. In this paper, Simulations based on Oxide TFT device model have demonstrated that the flexible computing parts could perform 5 × 5 Gaussian convolution operation at a speed of 3.3 MOPS/s with the energy efficiency of 1.83 TOPS/J, and realize image classification at a speed of 10 k fps, with the energy efficiency of 5.25 GOPS/J, which means that the potential applications to realize real-time computing parts of complex algorithms with flexible electronic devices, as well as the future fully flexible systems containing sensors, data converters, energy suppliers, and real-time signal processing modules, all with flexible devices. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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2680 KiB

Open AccessArticle

Amorphous Oxide Thin Film Transistors with Nitrogen-Doped Hetero-Structure Channel Layers

by Haiting Xie, Guochao Liu, Lei Zhang, Yan Zhou and Chengyuan Dong

Appl. Sci. 2017, 7(10), 1099; https://0-doi-org.brum.beds.ac.uk/10.3390/app7101099 - 24 Oct 2017

Cited by 19 | Viewed by 7688

Abstract

The nitrogen-doped amorphous oxide semiconductor (AOS) thinfilm transistors (TFTs) with double-stacked channel layers (DSCL) were prepared and characterized. The DSCL structure was composed of nitrogen-doped amorphous InGaZnO and InZnO films (a-IGZO:N/a-IZO:N or a-IZO:N/a-IGZO:N) and gave the corresponding TFT devices large field-effect mobility due [...] Read more.

The nitrogen-doped amorphous oxide semiconductor (AOS) thinfilm transistors (TFTs) with double-stacked channel layers (DSCL) were prepared and characterized. The DSCL structure was composed of nitrogen-doped amorphous InGaZnO and InZnO films (a-IGZO:N/a-IZO:N or a-IZO:N/a-IGZO:N) and gave the corresponding TFT devices large field-effect mobility due to the presence of double conduction channels. The a-IZO:N/a-IGZO:N TFTs, in particular, showed even better electrical performance (µ_FE = 15.0 cm²・V⁻¹・s⁻¹, SS = 0.5 V/dec, V_TH = 1.5 V, I_ON/I_OFF = 1.1 × 10⁸) and stability (V_TH shift of 1.5, −0.5 and −2.5 V for positive bias-stress, negative bias-stress, and thermal stress tests, respectively) than the a-IGZO:N/a-IZO:N TFTs. Based on the X-ray photoemission spectroscopy measurements and energy band analysis, we assumed that the optimized interface trap states, the less ambient gas adsorption, and the better suppression of oxygen vacancies in the a-IZO:N/a-IGZO:N hetero-structures might explain the better behavior of the corresponding TFTs. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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3850 KiB

Open AccessArticle

Reduction of Bias and Light Instability of Mixed Oxide Thin-Film Transistors

by Mallory Mativenga, Jae Gwang Um and Jin Jang

Appl. Sci. 2017, 7(9), 885; https://0-doi-org.brum.beds.ac.uk/10.3390/app7090885 - 29 Aug 2017

Cited by 26 | Viewed by 8438

Abstract

Despite their potential use as pixel-switching elements in displays, the bias and light instability of mixed oxide semiconductor thin-film transistors (TFTs) still limit their application to commercial products. Lack of reproducible results due to the sensitivity of the mixed oxides to air exposure [...] Read more.

Despite their potential use as pixel-switching elements in displays, the bias and light instability of mixed oxide semiconductor thin-film transistors (TFTs) still limit their application to commercial products. Lack of reproducible results due to the sensitivity of the mixed oxides to air exposure and chemical contamination during or after fabrication hinders any progress towards the achievement of stable performance. Consequently, one finds in literature several theories and mechanisms, all justified, but most of them conflict despite being on the same subject matter. In this study, we show that under an optimized fabrication process, which involves the in situ passivation of a mixed oxide semiconductor, we can reduce the bias and light instability of the mixed-oxide semiconductor TFTs by decreasing the semiconductor thickness. We achieve a negligible threshold voltage shift under negative bias combined with light illumination stress when the mixed oxide semiconductor thickness is around three nanometers. The improvement of stability in the thin mixed-oxide semiconductor TFTs is due to a reduced number of oxygen-vacancy defects in the bulk of the semiconductor, as their total number decreases with decreasing thickness. Under the optimized fabrication process, bulk, rather than interfacial defects, thus seem to be the main source of the bias and light instability in mixed oxide TFTs. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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2075 KiB

Open AccessArticle

Amorphous InGaZnO Thin Film Transistor Fabricated with Printed Silver Salt Ink Source/Drain Electrodes

by Caigui Yang, Zhiqiang Fang, Honglong Ning, Ruiqiang Tao, Jianqiu Chen, Yicong Zhou, Zeke Zheng, Rihui Yao, Lei Wang, Junbiao Peng and Yongsheng Song

Appl. Sci. 2017, 7(8), 844; https://0-doi-org.brum.beds.ac.uk/10.3390/app7080844 - 16 Aug 2017

Cited by 16 | Viewed by 5783

Abstract

Recently, amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) with inkjet printing silver source/drain electrodes have attracted great attention, especially for large area and flexible electronics applications. The silver ink could be divided into two types: one is based on silver nanoparticles, and the [...] Read more.

Recently, amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) with inkjet printing silver source/drain electrodes have attracted great attention, especially for large area and flexible electronics applications. The silver ink could be divided into two types: one is based on silver nanoparticles, and the other is silver salt ink. Organic materials are essential in the formulation of nanoparticle ink as a strong disperse stabilizer to prevent agglomeration of silver particles, but will introduce contact problems between the silver electrodes and the a-IGZO active layer after annealing, which is difficult to eliminate and leads to poor device properties. Our experiment is aimed to reduce this effect by using a silver salt ink without stabilizer component. With optimized inkjet printing conditions, the high performance of a-IGZO TFT was obtained with a mobility of 4.28 cm²/V·s and an on/off current ratio over 10⁶. The results have demonstrated a significant improvement for a-IGZO TFTs with directly printed silver electrodes. This work presents a promising platform for future printed electronic applications. Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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3029 KiB

Open AccessArticle

High Conductivity and Adhesion of Cu-Cr-Zr Alloy for TFT Gate Electrode

by Junbiao Peng, Kuankuan Lu, Shiben Hu, Zhiqiang Fang, Honglong Ning, Jinglin Wei, Zhennan Zhu, Yicong Zhou, Lei Wang, Rihui Yao and Xubing Lu

Appl. Sci. 2017, 7(8), 820; https://0-doi-org.brum.beds.ac.uk/10.3390/app7080820 - 10 Aug 2017

Cited by 7 | Viewed by 5242

Abstract

The characteristics of Cu alloy (0.3 wt. % Cr, 0.2 wt. % Zr) thin film deposited by direct current (DC) magnetron sputtering deposition were investigated. The conductivity and adhesion of the Cu-0.3%Cr-0.2%Zr films were optimized by increasing the sputter power to 150 W [...] Read more.

The characteristics of Cu alloy (0.3 wt. % Cr, 0.2 wt. % Zr) thin film deposited by direct current (DC) magnetron sputtering deposition were investigated. The conductivity and adhesion of the Cu-0.3%Cr-0.2%Zr films were optimized by increasing the sputter power to 150 W and reducing the sputter pressure to 2 mTorr. With an annealing process (at 300 °C for 1 h in argon ambient atmosphere), the resistivity of the alloy film decreased from 4.80 to 2.96 μΩ·cm, and the adhesion classification increased from 2B to 4B on glass substrate. X-ray photoelectron spectroscopy (XPS) analysis showed that Cr aggregated toward the surface of the film and formed a self-protection layer in the annealing process. Transmission electron microscopy (TEM) indicated the aggregation and migration of Cr in the annealing process. A further X-ray diffraction (XRD) analysis showed that Cu₂O appeared when the annealing temperature reached above 350 °C, which accounts for the increase of the resistivity. Based on Al₂O₃ and SiO₂ substrate surfaces, the Cu-0.3%Cr-0.2%Zr film also showed high conductivity and adhesion, which has a potential in the application of Cu gate electrodes for thin film transistor (TFT). Full article

(This article belongs to the Special Issue Thin-Film Transistor)

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