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Open AccessArticle

Enhancing the Carrier Mobility and Bias Stability in Metal–Oxide Thin Film Transistors with Bilayer InSnO/a-InGaZnO Heterojunction Structure

by Xiaoming Huang, Chen Chen, Fei Sun, Xinlei Chen, Weizong Xu and Lin Li

Micromachines 2024, 15(4), 512; https://doi.org/10.3390/mi15040512 - 11 Apr 2024

Cited by 7 | Viewed by 3907

Abstract

In this study, the electrical performance and bias stability of InSnO/a-InGaZnO (ITO/a-IGZO) heterojunction thin-film transistors (TFTs) are investigated. Compared to a-IGZO TFTs, the mobility (µ_FE) and bias stability of ITO/a-IGZO heterojunction TFTs are enhanced. The band alignment of the ITO/a-IGZO [...] Read more.

In this study, the electrical performance and bias stability of InSnO/a-InGaZnO (ITO/a-IGZO) heterojunction thin-film transistors (TFTs) are investigated. Compared to a-IGZO TFTs, the mobility (µ_FE) and bias stability of ITO/a-IGZO heterojunction TFTs are enhanced. The band alignment of the ITO/a-IGZO heterojunction is analyzed by using X-ray photoelectron spectroscopy (XPS). A conduction band offset (∆E_C) of 0.5 eV is observed in the ITO/a-IGZO heterojunction, resulting in electron accumulation in the formed potential well. Meanwhile, the ∆E_C of the ITO/a-IGZO heterojunction can be modulated by nitrogen doping ITO (ITON), which can affect the carrier confinement and transport properties at the ITO/a-IGZO heterojunction interface. Moreover, the carrier concentration distribution at the ITO/a-IGZO heterointerface is extracted by means of TCAD silvaco 2018 simulation, which is beneficial for enhancing the electrical performance of ITO/a-IGZO heterojunction TFTs. Full article

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11 pages, 5555 KB

Open AccessArticle

355 nm Nanosecond Ultraviolet Pulsed Laser Annealing Effects on Amorphous In-Ga-ZnO Thin Film Transistors

by Sang Yeon Park, Younggon Choi, Yong Hyeok Seo, Hojun Kim, Dong Hyun Lee, Phuoc Loc Truong, Yongmin Jeon, Hocheon Yoo, Sang Jik Kwon, Daeho Lee and Eou-Sik Cho

Micromachines 2024, 15(1), 103; https://doi.org/10.3390/mi15010103 - 5 Jan 2024

Cited by 9 | Viewed by 4473

Abstract

Bottom-gate thin-film transistors (TFTs) with n-type amorphous indium-gallium-zinc oxide (a-IGZO) active channels and indium-tin oxide (ITO) source/drain electrodes were fabricated. Then, an ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was scanned to locally anneal the active channel at various [...] Read more.

Bottom-gate thin-film transistors (TFTs) with n-type amorphous indium-gallium-zinc oxide (a-IGZO) active channels and indium-tin oxide (ITO) source/drain electrodes were fabricated. Then, an ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was scanned to locally anneal the active channel at various laser powers. After laser annealing, negative shifts in the threshold voltages and enhanced on-currents were observed at laser powers ranging from 54 to 120 mW. The energy band gap and work function of a-IGZO extracted from the transmittance and ultraviolet photoelectron spectroscopy (UPS) measurement data confirm that different energy band structures for the ITO electrode/a-IGZO channel were established depending on the laser annealing conditions. Based on these observations, the electron injection mechanism from ITO electrodes to a-IGZO channels was analyzed. The results show that the selective laser annealing process can improve the electrical performance of the a-IGZO TFTs without any thermal damage to the substrate. Full article

(This article belongs to the Special Issue Wearable Organic Electronics and Applications)

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13 pages, 4648 KB

Open AccessEditor’s ChoiceArticle

Monolithic Integration of Semi-Transparent and Flexible Integrated Image Sensor Array with a-IGZO Thin-Film Transistors (TFTs) and p-i-n Hydrogenated Amorphous Silicon Photodiodes

by Donghyeong Choi, Ji-Woo Seo, Jongwon Yoon, Seung Min Yu, Jung-Dae Kwon, Seoung-Ki Lee and Yonghun Kim

Nanomaterials 2023, 13(21), 2886; https://doi.org/10.3390/nano13212886 - 31 Oct 2023

Cited by 3 | Viewed by 3970

Abstract

A novel approach to fabricating a transparent and flexible one-transistor–one-diode (1T-1D) image sensor array on a flexible colorless polyimide (CPI) film substrate is successfully demonstrated with laser lift-off (LLO) techniques. Leveraging transparent indium tin oxide (ITO) electrodes and amorphous indium gallium zinc oxide [...] Read more.

A novel approach to fabricating a transparent and flexible one-transistor–one-diode (1T-1D) image sensor array on a flexible colorless polyimide (CPI) film substrate is successfully demonstrated with laser lift-off (LLO) techniques. Leveraging transparent indium tin oxide (ITO) electrodes and amorphous indium gallium zinc oxide (a-IGZO) channel-based thin-film transistor (TFT) backplanes, vertically stacked p-i-n hydrogenated amorphous silicon (a-Si:H) photodiodes (PDs) utilizing a low-temperature (<90 °C) deposition process are integrated with a densely packed 14 × 14 pixel array. The low-temperature-processed a-Si:H photodiodes show reasonable performance with responsivity and detectivity for 31.43 mA/W and 3.0 × 10¹⁰ Jones (biased at −1 V) at a wavelength of 470 nm, respectively. The good mechanical durability and robustness of the flexible image sensor arrays enable them to be attached to a curved surface with bending radii of 20, 15, 10, and 5 mm and 1000 bending cycles, respectively. These studies show the significant promise of utilizing highly flexible and rollable active-matrix technology for the purpose of dynamically sensing optical signals in spatial applications. Full article

(This article belongs to the Special Issue Low-Dimensional Nanostructures: Synthesis, Characterization and Applications)

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10 pages, 9044 KB

Open AccessArticle

Effects of Source/Drain Electrodes on the Performance of InSnO Thin-Film Transistors

by Qi Li, Dedong Han, Junchen Dong, Dengqin Xu, Yue Li, Yi Wang and Xing Zhang

Micromachines 2022, 13(11), 1896; https://doi.org/10.3390/mi13111896 - 2 Nov 2022

Cited by 7 | Viewed by 3667

Abstract

Oxide thin-film transistors (TFTs) are of increasing interest in the field of advanced displays. In this work, we explore Al, InSnO (ITO), Ti, and Mo as source/drain electrodes of ITO TFTs. A comparison study is conducted on the electrical properties of ITO TFTs [...] Read more.

Oxide thin-film transistors (TFTs) are of increasing interest in the field of advanced displays. In this work, we explore Al, InSnO (ITO), Ti, and Mo as source/drain electrodes of ITO TFTs. A comparison study is conducted on the electrical properties of ITO TFTs with the four categories of source/drain electrodes. Interestingly, the ITO TFT with an Al source/drain electrode exhibits better device performance, such as a field-effect mobility (μ_FE) of 26.45 cm²/Vs, a reasonable turn-on voltage (V_ON) of 2.7 V, and a steep subthreshold swing (SS) of 201.50 mV/decade. The contact properties of ITO TFTs are further analyzed, and the results show that the device with an Al electrode exhibits lower contact resistance than the other devices. However, the devices with the four electrode materials all reveal excellent stability under negative bias illumination stress (NBIS) with |ΔV_TH| < 1 V. This work paves the way for the practical applications of ITO TFTs in next-generation displays. Full article

(This article belongs to the Special Issue Recent Advances in Thin Film Transistors)

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10 pages, 5403 KB

Open AccessArticle

Structural Engineering Effects on Hump Characteristics of ZnO/InSnO Heterojunction Thin-Film Transistors

by Qi Li, Junchen Dong, Dedong Han, Dengqin Xu, Jingyi Wang and Yi Wang

Nanomaterials 2022, 12(7), 1167; https://doi.org/10.3390/nano12071167 - 31 Mar 2022

Cited by 4 | Viewed by 2558

Abstract

Transparent conductive oxides (TCO) have been extensively investigated as channel materials for thin-film transistors (TFTs). In this study, highly transparent and conductive InSnO (ITO) and ZnO films were deposited, and their material properties were studied in detail. Meanwhile, we fabricated ZnO/ITO heterojunction TFTs, [...] Read more.

Transparent conductive oxides (TCO) have been extensively investigated as channel materials for thin-film transistors (TFTs). In this study, highly transparent and conductive InSnO (ITO) and ZnO films were deposited, and their material properties were studied in detail. Meanwhile, we fabricated ZnO/ITO heterojunction TFTs, and explored the effects of channel structures on the hump characteristics of ZnO/ITO TFTs. We found that V_hump–V_ON was negatively correlated with the thickness of the bottom ZnO layer (10, 20, 30, and 40 nm), while it was positively correlated with the thickness of the top ITO layer (3, 5, 7, and 9 nm), where V_hump is the gate voltage corresponding to the occurrence of the hump and V_ON is the turn-on voltage. The results demonstrated that carrier transport forms dual current paths through both the ZnO and ITO layers, synthetically determining the hump characteristics of the ZnO/ITO TFTs. Notably, the hump was effectively eliminated by reducing the ITO thickness to no more than 5 nm. Furthermore, the hump characteristics of the ZnO/ITO TFTs under positive gate-bias stress (PBS) were examined. This work broadens the practical application of TCO and provides a promising method for solving the hump phenomenon of oxide TFTs. Full article

(This article belongs to the Special Issue Transparent Conductive Nanomaterials: Science and Applications)

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10 pages, 12405 KB

Open AccessArticle

Effects of Channel Thickness on Electrical Performance and Stability of High-Performance InSnO Thin-Film Transistors

by Qi Li, Junchen Dong, Dedong Han and Yi Wang

Membranes 2021, 11(12), 929; https://doi.org/10.3390/membranes11120929 - 26 Nov 2021

Cited by 21 | Viewed by 3614

Abstract

InSnO (ITO) thin-film transistors (TFTs) attract much attention in fields of displays and low-cost integrated circuits (IC). In the present work, we demonstrate the high-performance, robust ITO TFTs that fabricated at process temperature no higher than 100 °C. The influences of channel thickness [...] Read more.

InSnO (ITO) thin-film transistors (TFTs) attract much attention in fields of displays and low-cost integrated circuits (IC). In the present work, we demonstrate the high-performance, robust ITO TFTs that fabricated at process temperature no higher than 100 °C. The influences of channel thickness (t_ITO, respectively, 6, 9, 12, and 15 nm) on device performance and positive bias stress (PBS) stability of the ITO TFTs are examined. We found that content of oxygen defects positively correlates with t_ITO, leading to increases of both trap states as well as carrier concentration and synthetically determining electrical properties of the ITO TFTs. Interestingly, the ITO TFTs with a t_ITO of 9 nm exhibit the best performance and PBS stability, and typical electrical properties include a field-effect mobility (µ_FE) of 37.69 cm²/Vs, a V_on of −2.3 V, a SS of 167.49 mV/decade, and an on–off current ratio over 10⁷. This work paves the way for practical application of the ITO TFTs. Full article

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

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8 pages, 1899 KB

Open AccessArticle

Influence of Hydrogen Ions on the Performance of Thin-Film Transistors with Solution-Processed AlO_x Gate Dielectrics

by Yongbo Wu, Linfeng Lan, Penghui He, Yilong Lin, Caihao Deng, Siting Chen and Junbiao Peng

Appl. Sci. 2021, 11(10), 4393; https://doi.org/10.3390/app11104393 - 12 May 2021

Cited by 9 | Viewed by 2814

Abstract

Over the past decade, there have been many reports on solution-processed oxide thin-film transistors (TFTs) with high mobility (even >100 cm² V⁻¹s⁻¹). However, the capacitance uncertainty of the solution-processed oxide gate dielectrics leads to serious overestimation of the [...] Read more.

Over the past decade, there have been many reports on solution-processed oxide thin-film transistors (TFTs) with high mobility (even >100 cm² V⁻¹s⁻¹). However, the capacitance uncertainty of the solution-processed oxide gate dielectrics leads to serious overestimation of the mobility. Here, solution-processed AlO_x dielectrics are investigated systematically, and the effect of mobile ions on the frequency-dependent capacitance of the solution-processed AlO_x dielectrics is also studied. It was found that the capacitance of the AlO_x depends on the frequency seriously when the annealing temperature is lower than 300 °C, and the water treatment causes more seriously frequency-dependent capacitance. The strong frequency-dependent capacitance of the AlO_x annealed at 250 or 300 °C is attributed to relaxation polarization of the weakly bound ions in the incompletely decomposed AlO_x films. The water treatment introduces a large number of protons (H⁺) that would migrate to the ITO/AlO_x interface under a certain electric field and form an electric double layer (EDL) that has ultrahigh capacitance at low frequency. Full article

(This article belongs to the Section Materials Science and Engineering)

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9 pages, 8650 KB

Open AccessArticle

Fully Inkjet-Printed Short-Channel Metal-Oxide Thin-Film Transistors Based on Semitransparent ITO/Au Source/Drain Electrodes

by Yuzhi Li and Shengdong Zhang

Coatings 2020, 10(10), 942; https://doi.org/10.3390/coatings10100942 - 30 Sep 2020

Cited by 2 | Viewed by 3710

Abstract

In this work, short-channel semitransparent indium-tin-oxide (ITO)/Au electrode pairs were fabricated via inkjet printing and lift-off technology. The printed hydrophobic coffee stripes not only define the channel length of ITO/Au electrode pairs, but also help the realization of uniform short-channel In_0.95Ga [...] Read more.

In this work, short-channel semitransparent indium-tin-oxide (ITO)/Au electrode pairs were fabricated via inkjet printing and lift-off technology. The printed hydrophobic coffee stripes not only define the channel length of ITO/Au electrode pairs, but also help the realization of uniform short-channel In_0.95Ga_0.05O_x thin-film transistors (TFTs). The patterned semitransparent ITO/Au films, with the assistance of inkjet printing, exhibit an excellent conductivity compared to that of printed ITO films, and the short-channel In_0.95Ga_0.05O_x TFTs based on the semitransparent ITO/Au source/drain electrodes exhibit a maximum mobility of 2.9 cm² V⁻¹ s⁻¹. This work proposes a method to prepare patterned high-conductive electrodes for TFTs with the assistance of inkjet printing. Full article

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8 pages, 2530 KB

Open AccessArticle

Bendable Single Crystal Silicon Nanomembrane Thin Film Transistors with Improved Low-Temperature Processed Metal/n-Si Ohmic Contact by Inserting TiO₂ Interlayer

by Jiaqi Zhang, Yi Zhang, Dazheng Chen, Weidong Zhu, He Xi, Jincheng Zhang, Chunfu Zhang and Yue Hao

Nanomaterials 2018, 8(12), 1060; https://doi.org/10.3390/nano8121060 - 16 Dec 2018

Cited by 5 | Viewed by 5404

Abstract

Bendable single crystal silicon nanomembrane thin film transistors (SiNMs TFTs), employing a simple method which can improve the metal/n-Silicon (Si) contact characteristics by inserting the titanium dioxide (TiO₂) interlayer deposited by atomic layer deposition (ALD) at a low temperature (90 °C), [...] Read more.

Bendable single crystal silicon nanomembrane thin film transistors (SiNMs TFTs), employing a simple method which can improve the metal/n-Silicon (Si) contact characteristics by inserting the titanium dioxide (TiO₂) interlayer deposited by atomic layer deposition (ALD) at a low temperature (90 °C), are fabricated on ITO/PET flexible substrates. Current-voltage characteristics of titanium (Ti)/insertion layer (IL)/n-Si structures demonstrates that they are typically ohmic contacts. X-ray photoelectron spectroscopy (XPS) results determines that TiO₂ is oxygen-vacancies rich, which may dope TiO₂ and contribute to a lower resistance. By inserting TiO₂ between Ti and n-Si, I_ds of bendable single crystal SiNMs TFTs increases 3–10 times than those without the TiO₂ insertion layer. The fabricated bendable devices show superior flexible properties. The TFTs, whose electrical properties keeps almost unchanged in 800 cycles bending with a bending radius of 0.75 cm, obtains the durability in bending test. All of the results confirm that it is a promising method to insert the TiO₂ interlayer for improving the Metal/n-Si ohmic contact in fabrication of bendable single crystal SiNMs TFTs. Full article

(This article belongs to the Special Issue Silicon-Based Nanomaterials: Technology and Applications)

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8 pages, 2125 KB

Open AccessArticle

Effect of Source/Drain Electrodes on the Electrical Properties of Silicon–Tin Oxide Thin-Film Transistors

by Xianzhe Liu, Honglong Ning, Weifeng Chen, Zhiqiang Fang, Rihui Yao, Xiaofeng Wang, Yuxi Deng, Weijian Yuan, Weijing Wu and Junbiao Peng

Nanomaterials 2018, 8(5), 293; https://doi.org/10.3390/nano8050293 - 2 May 2018

Cited by 9 | Viewed by 6229

Abstract

Ultra-high definition displays have become a trend for the current flat plane displays. In this study, the contact properties of amorphous silicon–tin oxide thin-film transistors (a-STO TFTs) employed with source/drain (S/D) electrodes were analyzed. Ohmic contact with a good device performance was achieved [...] Read more.

Ultra-high definition displays have become a trend for the current flat plane displays. In this study, the contact properties of amorphous silicon–tin oxide thin-film transistors (a-STO TFTs) employed with source/drain (S/D) electrodes were analyzed. Ohmic contact with a good device performance was achieved when a-STO was matched with indium-tin-oxide (ITO) or Mo electrodes. The acceptor-like densities of trap states (DOS) of a-STO TFTs were further investigated by using low-frequency capacitance–voltage (C–V) characteristics to understand the impact of the electrode on the device performance. The reason of the distinct electrical performances of the devices with ITO and Mo contacts was attributed to different DOS caused by the generation of local defect states near the electrodes, which distorted the electric field distribution and formed an electrical potential barrier hindering the flow of electrons. It is of significant importance for circuit designers to design reliable integrated circuits with SnO₂-based devices applied in flat panel displays. Full article

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10 pages, 2410 KB

Open AccessArticle

An All Oxide-Based Imperceptible Thin-Film Transistor with Humidity Sensing Properties

by Kyung Su Kim, Cheol Hyoun Ahn, Won Jun Kang, Sung Woon Cho, Sung Hyeon Jung, Dae Ho Yoon and Hyung Koun Cho

Materials 2017, 10(5), 530; https://doi.org/10.3390/ma10050530 - 13 May 2017

Cited by 22 | Viewed by 6960

Abstract

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O [...] Read more.

We have examined the effects of oxygen content and thickness in sputtered InSnO (ITO) electrodes, especially for the application of imperceptible amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) in humidity sensors. The imperceptible a-IGZO TFT with 50-nm ITO electrodes deposited at Ar:O₂ = 29:0.3 exhibited good electrical performances with V_th of −0.23 V, SS of 0.34 V/dec, µ_FE of 7.86 cm²/V∙s, on/off ratio of 8.8 × 10⁷, and has no degradation for bending stress up to a 3.5-mm curvature. The imperceptible oxide TFT sensors showed the highest sensitivity for the low and wide gate bias of −1~2 V under a wide range of relative humidity (40–90%) at drain voltage 1 V, resulting in low power consumption by the sensors. Exposure to water vapor led to a negative shift in the threshold voltage (or current enhancement), and an increase in relative humidity induced continuous threshold voltage shift. In particular, compared to conventional resistor-type sensors, the imperceptible oxide TFT sensors exhibited extremely high sensitivity from a current amplification of >10³. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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8 pages, 527 KB

Open AccessArticle

Characteristics of Indium Tin Oxide (ITO) Nanoparticles Recovered by Lift-off Method from TFT-LCD Panel Scraps

by Dongchul Choi, Sung-Jei Hong and Yongkeun Son

Materials 2014, 7(12), 7662-7669; https://doi.org/10.3390/ma7127662 - 27 Nov 2014

Cited by 66 | Viewed by 12834

Abstract

In this study, indium-tin-oxide (ITO) nanoparticles were simply recovered from the thin film transistor-liquid crystal display (TFT-LCD) panel scraps by means of lift-off method. This can be done by dissolving color filter (CF) layer which is located between ITO layer and glass substrate. [...] Read more.

In this study, indium-tin-oxide (ITO) nanoparticles were simply recovered from the thin film transistor-liquid crystal display (TFT-LCD) panel scraps by means of lift-off method. This can be done by dissolving color filter (CF) layer which is located between ITO layer and glass substrate. In this way the ITO layer was easily lifted off the glass substrate of the panel scrap without panel crushing. Over 90% of the ITO on the TFT-LCD panel was recovered by using this method. After separating, the ITO was obtained as particle form and their characteristics were investigated. The recovered product appeared as aggregates of particles less than 100 nm in size. The weight ratio of In/Sn is very close to 91/9. XRD analysis showed that the ITO nanoparticles have well crystallized structures with (222) preferred orientation even after recovery. The method described in this paper could be applied to the industrial recovery business for large size LCD scraps from TV easily without crushing the glass substrate. Full article

(This article belongs to the Special Issue Recycled Materials)

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