Layer In Thin Film Transistors Research Articles

In Situ Radiation Hardness Study of Amorphous Zn-In-Sn-O Thin-Film Transistors with Structural Plasticity and Defect Tolerance.

Solution-processed metal-oxide thin-film transistors (TFTs) with different metal compositions are investigated for ex situ and in situ radiation hardness experiments against ionizing radiation exposure. The synergetic combination of structural plasticity of Zn, defect tolerance of Sn, and high electron mobility of In identifies amorphous zinc-indium-tin oxide (Zn-In-Sn-O or ZITO) as an optimal radiation-resistant channel layer of TFTs. The ZITO with an elemental blending ratio of 4:1:1 for Zn/In/Sn exhibits superior ex situ radiation resistance compared to In-Ga-Zn-O, Ga-Sn-O, Ga-In-Sn-O, and Ga-Sn-Zn-O. Based on the in situ irradiation results, where a negative threshold voltage shifts and a mobility increase as well as both off current and leakage current increase are observed, three factors are proposed for the degradation mechanisms: (i) increase of channel conductivity, (ii) interface-trapped and dielectric-trapped charge buildup, and (iii) trap-assisted tunneling in the dielectric. Finally, in situ radiation-hard oxide-based TFTs are demonstrated by employing a radiation-resistant ZITO channel, a thin dielectric (50 nm SiO2), and a passivation layer (PCBM for ambient exposure), which exhibit excellent stability with an electron mobility of ∼10 cm2/V s and aΔVth of <3 V under real-time (15 kGy/h) gamma-ray irradiation in an ambient atmosphere.

Benefits from Using Very Thin Channel Layer for TFTs

It is known from many published data on amorphous or polycrystalline silicon and on metal oxides based Thin Film Transistors (TFTs) that their electrical parameters improve when decreasing the thickness of the channel layer. The origin of this improvement is discussed here through electrostatic arguments only. In particular, it is shown that the behavior of the subthreshold swing with the thickness does not depend on the type of materials. The material and its electrical defects determine only the importance of the improvement but not the trend towards better electrical parameters. Meanwhile, in general, the electrical stability under gate stress enhances too. The improved stability is explained by the reduced electronic charge inside the channel layer, leading to a lower injection of electrons in the gate insulator.

Highly sensitive biosensor based on IGZO thin-film transistors for detection of Parkinson's disease

α-Synuclein (α-Syn) is a major biomarker of Parkinson's disease (PD). Concentration detection of α-Syn in cerebrospinal fluid and plasma of patients are used as a clue for early PD detection. Herein, we propose a thin-film transistor (TFT) biosensor based on an indium gallium zinc oxide (IGZO) thin film fabricated by the sol-gel method. The IGZO TFT biosensor is used for the early detection of PD after surface functionalization for α-Syn. The surface functionalization worked on the surface of the extended gate indium tin oxide sensing platform instead of the channel layer of TFT. Depending on concentrations of α-Syn in human cerebrospinal fluid and plasma, we diluted six different concentrations of α-Syn for detection, ranging from 1 pg ml−1 to 100 ng ml−1. The result shows that the biosensor exhibits high sensitivity and selectivity for α-Syn, a reliable sensing performance with a sensitivity of 189.9 mV dec−1, and a coefficient of determination R2 of 99.7% between 10 pg ml−1 and 100 ng ml−1.

The improved properties of solution-based InGaSnO (IGTO) thin film transistor using the modification of InZnO (IZO) layer

For improving the properties of indium-gallium-tin oxide (IGTO) thin film transistors (TFTs) based on solution method, indium-zinc oxide (IZO) thin film was used as a modification layer. When IZO did not perform post-annealing, the performance improvement of bilayer TFTs was not significant. When IZO performed post-annealing, the performance improvement of the bilayer TFTs was obvious. We also compared the effects of annealing time on the performance of IGTO TFTs. The modifying effects of IZO and the suitable annealing time led to a great improvement in the performance of TFTs. The mobility was increased by about 10 times than monolayer IGTO (0.27 cm2V−1s−1→4.38 cm2V−1s−1), and the threshold voltage and subthreshold swing were also very small (0.60 V, 0.55). We attribute the performance improvement of dual active layer TFTs to two reasons. On the one hand, the modifying effects of IZO made the IGTO defect state less and the film denser. On the other hand, the bilayer TFTs form a heterojunction structure similar to 2-dimensional electron gas (2DEG), which enhanced the mobility of the TFTs. This paper provides a research basis for the process of preparing dual active layers by solution method, and provides a new idea for the performance improvement of IGTO.

Fabrication of transparent polycrystalline zinc oxide thin film UV sensing transistor using polymeric electrolyte gate dielectric

The fabrication of electric double layer thin film transistors (EDLTFTs) using polymeric electrolyte as gate dielectric on chemically grown polycrystalline ZnO thin film channel has the lower threshold voltage at 0.4 V and the saturation current at 3 µA in the dark. The lower threshold voltage is -1 V and the saturation current is 10 µA in the UV illumination. In the dark and under UV light, the off state ID is 1 nA and 0.3 µA respectively and under gate and UV illumination the on current shows more than 3 times enhancement. This improvement in photocurrent is due to the combined effect of gate and UV illumination. The field effect mobility of the TFT is 0.06 cm2/Vs in the dark and 0.16 cm2/Vs under UV illumination. This increase in mobility under illumination and gate bias is due to the increase in carrier concentration and reduction of charged defects in the channel length.

Experimental and Theoretical Evidence of Charge Injection Barrier Control by Small-Molecular Charge Injection Layer and Its Effects on Organic–Inorganic Complementary Inverters

Introducing a contact charge injection layer at the interface between the contact electrode and active materials is considered crucial to obtain efficient charge injection behaviors in thin-film transistors (TFTs). Here, we investigate the effect of a small molecule contact charge injection layer through experimental results and theoretical calculations. We found limited electrical characteristics derived from contact resistance in C8-BTBT TFTs with C8-BTBT as the channel and Au as the electrode. We experimentally demonstrated that the limited electrical characteristics of C8-BTBT TFT can be improved by inserting dinaphtho[2,3-b: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{\prime} $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{\prime} $ </tex-math></inline-formula> -f]thieno [3,2-b] thiophene (DNTT), which has a low contact resistance at the junction with Au, as a charge injection layer. The results of improved contact properties through the DNTT charge injection layer were also consistent with the results of energy structural simulations. Furthermore, we verified the effect of the DNTT charge injection layer at the circuit level through improved noise margin characteristics in the complementary inverter composed of asymmetric charge injection layer TFT (ACIL-TFT) and a-indium gallium zinc oxide (IGZO) TFT.

Physical Properties of an Ultrathin Al2O3/HfO2 Composite Film by Atomic Layer Deposition and the Application in Thin-Film Transistors

A high-quality ultrathin dielectric film is important in the field of microelectronics. We designed a composite structure composed of Al2O3/HfO2 with different Al2O3/HfO2 cycles prepared by atomic layer deposition (ALD) to obtain high-quality ultrathin (1-12 nm) dielectric films. Al2O3 protected HfO2 from interacting with the Si substrate and inhibited the crystallization of the HfO2 film. High permittivity material of HfO2 was adopted to guarantee the good insulating property of the composite film. We investigated the physical properties as well as the growth mode of the composite film and found that the film exhibited a layer growth mode. The water contact angle and grazing-incidence small-angle X-ray scattering analyses revealed that the film was formed physically at 3 nm, while the thickness of the electrically stable film was 10 nm from grazing-incidence wide-angle X-ray scattering and dielectric constant analyses. The composite film was applied as a dielectric layer in thin-film transistors (TFTs). The threshold voltage was decreased to 0.27 V compared to the organic field-effect transistor with the single HfO2 dielectric, and the subthreshold swing was as small as 0.05 V/dec with a carrier mobility of 49.2 cm2/V s. The off-current was as low as 10-11 A, and the on/off ratio was as high as 5.5 × 106. This ALD-prepared composite strategy provides a simple and practical way to obtain the high-quality dielectric film, which shows the potential application in the field of microelectronics.

Flexible, Transparent, High Mobility Amorphous In–Ga–Zn-O Thin Film Transistors Fabricated on Textile

To implement wearable textile displays (WTDs), it is essential that unique properties such as physical and chemical properties, aesthetics, and flexibility of the textile be maintained. Therefore, thin film transistors (TFTs) for WTDs should exhibit excellent electrical properties to enable 4K and 8K high resolution and high frame-rate (>120 Hz) displays while maintaining the properties of textiles. All layers of TFTs were formed by vacuum deposition and oxide-based transparent materials; amorphous In–Ga–Zn-O (a-IGZO), indium tin oxide (ITO), and Al2O3 were used. A transparent and flexible electrode with an ITO/Ag/ITO (IAI) structure was optimized and applied to the source/drain and gate. All processes were performed below 150 °C, and the wet-step was eliminated to prevent physical and chemical deformation of the substrate. The flexible, transparent, high mobility a-IGZO TFTs (FTH TFTs) for WTDs were fabricated on glass, polyethylene terephthalate (PET) film, and textile substrates, respectively. Their electrical performance, transparency, and flexibility were then compared. The textile-based TFTs showed transmittance of 72.98%, high mobility of 11.5 cm2/(V s), and an on/off ratio of 9.28 × 107 even in a low temperature process (<150 °C). In addition, the electrical properties of the textile-based TFTs were maintained despite testing entailing 1000 cycles of bending with a tensile strain of 0.8%. In particular, the FTH TFTs for WTDs were able to stably drive a red organic light-emitting diode on textile.

Initial Nucleation Approach for Large Grain-Size and High-Quality Microcrystalline Silicon Active Layer in Thin Film Transistors

High mobility and stability are critical factors for thin film transistor (TFT) device quality. These parameters are directly dependent on the crystalline structure of the active layer materials. In this paper, the early nucleation approach was performed for increasing the crystalline grain size of microcrystalline silicon (μc-Si:H) active layer for TFT device quality. The crystalline nucleation is delicately regulated in an intense hydrogen plasma environment using the plasma enhanced chemical vapor deposition (PECVD). When compared to μc-Si:H deposition without the nucleation approach, the crystalline volume factor of μc-Si:H increased from 60% to over 80% by using the nucleation technique. The nucleation increases the crystalline grain size by five orders of magnitude. Furthermore, the surface roughness of μc-Si:H is decreased from 13.7 nm to 7.1 nm. A forming-gas post-annealing treatment (≤400 °C) is used to minimize defect density. With a low microstructural factor, thermal-treated film quality improves dramatically. Nucleation approach is to be a simple and efficient for producing high-quality TFT devices.

Amorphous N-doped InSnZnO thin films deposited by RF sputtering for thin-film transistor application

N-doped InSnZnO (ITZO:N) thin films as the active layer of thin film transistors (TFTs) were prepared using radio frequency (RF) magnetron sputtering at room temperature.

Electrical Performance Enhancement and Low-Frequency Noise Estimation of In2O3-Based Thin Film Transistor Based on Doping Engineering

In this work, solution-derived InErO thin films were deposited to act as the channel layers of thin film transistors (TFTs). The effect of Er doping content on the morphology, oxygen defects, optical properties of indium oxide (In2O3) films, and electrical performance of InErO/Al2O3 TFTs was systematically investigated. Based on experimental results, it can be inferred that InErO-TFTs with 5% Er doping content has demonstrated improved electrical performance, including field effect mobility ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}$ </tex-math></inline-formula> ) of 17.55 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\,\,\cdot \,\,\text{V}^{-{1}}\,\,\cdot \,\,\text{s}^{-{1}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text{ON}}/{I} _{\text{OFF}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.70\times 10^{{7}}$ </tex-math></inline-formula> , a subthreshold swing (SS) of 0.16 V/dec and threshold voltage shift of 0.10 and 0.09 V under positive bias stress (PBS) and negative bias stress (NBS) for 1800 s, respectively. The illumination NBS (NBIS) measurements have indicated the degraded device stability by reducing the light wavelength, which can be due to the ionization of oxygen vacancies. Low-frequency noise (LFN) characterizations on devices have shown that the interfacial density of states of In2O3-based TFTs decreases after Er doping. To demonstrate the potential applications of InErO-TFTs in logic circuits, a resistor-loaded unipolar inverter based on InErO/Al2O3 has been integrated, demonstrating good dynamic response behavior and high gain of 10. These results have indicated the great potential of solution-driven InErO-based TFTs for future applications in low-cost and high-performance electronics.

High performance carbon nanotubes thin film transistors by selective ferric chloride doping

Single wall carbon nanotubes (SWNT) have been a significant research topic as active layers for thin film transistors (TFTs) due to their high charge carrier mobility beyond that of crystalline silicon. In this study, we report an effective approach to achieve a very high field-effect mobility and on/off ratio for solution processed semiconducting SWNT TFTs, by selective doping through contact with a thin ferric chloride (FeCl3) dopant layer. The semiconducting layer is formed by a double spin coating of the highly purified (>99%) high pressure carbon mono oxide (HiPCO) SWNT sorted by wrapping of poly (3-dodecylthiophene-2,5-diyl) (P3DDT). In order to achieve effective hole injection from the top Au source electrode without increasing the off-state drain current, less purified (98-99%) SWNTs produced by the plasma discharge process sorted by wrapping of poly (9,9-di-n-dodecylfluorene) (PFDD) are formed on the top of HiPCO film. Significantly improved TFT performance is achieved by the insertion of a few nanometers of a FeCl3 dopant layer at the semiconductor-contact interface. A significant high hole field-effect of 48.35 ± 3.11 cm2V−1s−1 (bare: 6.18 ± 0.87 cm2V−1s−1) with a reasonable on/off current ratio of 105, and low off current of ∼80 pA, are obtained by controlling the concentration of FeCl3 dopant (thickness = 1.5 nm) at the contact. Mobility is improved further at 2.5 nm thickness of the FeCl3 dopant layer resulting in a hole mobility of 177 ± 13.2 cm2 V−1s−1, an on/off ratio of 7.4 × 103, and off state current of 1.2 × 10−9 A.

(Invited, Digital Presentation) Nondegenerate Hydrogen-Doped Polycrystalline Indium Oxide (InOx:H) Thin Films for High-Mobility Thin Film Transistors

Transparent metal oxide semiconductors (OSs) have been extensively investigated for use as the active channel layer of thin film transistors (TFTs) for next-generation flat-panel displays, nonvolatile memories, image sensors, and pH sensors, to name a few. Among OSs, the amorphous In–Ga–Zn–O (IGZO) has attracted particular attention for TFT applications owing to its high field effect mobility (μFE) of more than 10 cm2V−1s−1, steep subthreshold swing (S.S.), extremely low off-state current, large-area uniformity, and good bias stress stability. Although the μFE of an IGZO TFT is approximately one order of magnitude higher than that of an amorphous Si TFT, further improvement of the μFE of OS TFTs is required to expand their range of applications as an alternative to polycrystalline Si TFT.Single-crystalline In2O3 has a Hall mobility as high as 160 cm2V−1s−1, which makes amorphous (a-) or polycrystalline (poly-) InOx a potential material for enhancing the μFE of OS TFTs. However, undoped InOx thin films is known as a degenerate semiconductor with high background electron density of over 1020 cm-3, which is attributed to the presence of native defects, such as oxygen vacancies, making them unsuitable for a channel material of OS TFTs. In this presentation, nondegenerate hydrogen-doped polycrystalline InOx (poly-InOx:H) thin films were successfully prepared by low-temperature solid phase crystallization (SPC). A degenerate amorphous InOx:H thin film was deposited by sputtering in Ar, O2, and H2 gases, and an amorphous to polycrystalline phase transition (SPC) of the film was achieved after PDA at more than 175 °C. By PDA at 250 °C in air, a nondegenerate poly-InOx:H film could be obtained with a carrier density as low as 2.4 × 1017 cm−3, which is approximately three orders of magnitude lower than that of the initial a-InOx:H film. The TFTs with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. A maximum μFE of 125.7 cm2V−1s−1 was exhibited by the TFT with the poly-InOx:H channel. The use of a nondegenerate poly-InOx:H film is a promising approach to boost the μFE of OS TFTs.

Dielectric Behaviour of PVP 360 and PVA for Thin Flexible Transistors Application

Despite important progress in the field of the thin flexible transistor (TFT)-based electronics, a major challenge still exist for organic TFTs to decrease the operating voltage, which is related to the properties of the dielectric and semiconductor layers from the OTFTs structure. In this paper, we present the electrical behavior of two biocompatible polymers, polyvinylpyrrolidone (PVP 360) and polyvinyl alcohol (PVA), regarding the application as insulating layer in thin-film transistors. The PVA and PVP 360 thin films were deposited onto epoxy resin copper double-sided layer and polyethylene tere-phthalate/Indium tin oxide (PET/ITO) substrates by sol-gel method, spin-coating technique. Two sol concentrations (1 and 5 wt. %) were prepared and the contact angle onto the used substrates was measured using a digital microscope camera. The obtained films have been characterized by scanning electron microscopy (SEM) and dielectrical behaviour. For electrical measurements, the metal-insulating-metal (MIM) structure was realized by cooper electrodes deposition at room temperature, onto the top of thin films, by magnetron sputtering method. The current (I) - applied voltage (from -5 to +5 V) curves were measured in air at room temperature (RT), using the Picoammeter homemade device. PVA and PVP 360 thin films showed low leakage currents with values within � 2 nA for �5 V range.

Combustion Synthesis and Polymer Doping of Metal Oxides for High-Performance Electronic Circuitry.

ConspectusTransparent conducting oxides (TCOs) are inorganic electrical conductors with optical band gaps greater than 3.3 eV. TCOs have been extensively explored in functional windows, touch screen applications, transparent displays, solar cells, and even electronic circuits. Amorphous metal oxide (a-MO) semiconductors are a TCO class that has made impressive progress since the first 2004 demonstration of their utility as the semiconducting layer in thin-film transistors (TFTs). Their excellent counterintuitive electron mobilities in the amorphous state fill the performance gap between amorphous silicon and polysilicon, widening TFT applicability to high-value products such as high-resolution flat panel displays and emerging flexible/wearable electronics. The possibility of solution processing MO "inks" from air-stable precursors, via roll-to-roll and high-throughput printing, further expands their appeal. However, most MO TFTs fabricated using solution-processing require postdeposition film annealing at elevated temperatures (>400 °C) to ensure high-quality films and stable charge transport. Thus, MO fabrication on and TFT integration with inexpensive and typically temperature-sensitive flexible polymer substrates remains challenging, as does reducing MO processing times to those acceptable for high-throughput semiconductor circuit manufacture. Consequently, new MO film processing methodologies are being developed to meet these requirements. Among them, science-based combustion synthesis (CS) and polymer doping are promising complementary approaches to optimize materials quality and manufacturing efficiency; they are the topic of this Account.This Account summarizes the progress in CS and MO polymer doping research, made largely at Northwestern University over the past decade, to create high-performance MO TFTs. Regarding CS, we begin with an overview of combustion precursor chemistry that strongly affects the resulting film quality and device performance. Then, single fuel and dual fuel combustion syntheses for diverse MO systems are discussed. Representative examples highlight recent advances, with a focus on the relationship between (co)fuel-oxidizer types/amounts, thermal behavior, film microstructure, and TFT performance. Next, the discussion focuses on polymer doping of several MO matrices as a new approach to achieve semiconducting MO compositions with excellent performance and mechanical flexibility. Thus, the effect of the polymer architecture and content in the MO precursor formulations on the MO film composition, microstructure, electronic structure, and charge transport are discussed. The concluding remarks highlight challenges and emerging opportunities.

Environmentally friendly, flexible and high performance PVA dielectric layer fabricated by solution method and its application in IGZO-TFT

At present, Poly (Vinyl Alcohol) (PVA)is often used as the dielectric layer of thin film transistors (TFT)because of its good insulation and environmental protection. However, because of the hydroxyl groups on the surface, PVA films have poor contact with electrodes and semiconductors. Therefore, in this paper, we proposed an effective way to make PVA molecules curled up by applying dual solvent system with water and ethanol. As a result, the leakage current density is reduced from 1.2 × 10 −4 A/cm [2]@0.5 mV/cm to 6.2 × 10 −6 A/cm [2]@0.5 mV/cm. Moreover, we adjusted the molecular morphology of PVA in the solution by optimizing the configuration sequence of the precursor solution, so as to obtain a PVA film with better performance, with a leakage current density of only 5.9 × 10 −7 A/cm [2]@0.5 mV/cm. The change in molecular morphology can be seen from the solution viscosity and surface tension measurements. Finally, we prepared IGZO-TFT devices for comparison, and it is proved that the PVA films prepared after changing the configuration sequence have better application in TFT, with a mobility of 8.19 cm 2 V −1 s −1 and a switching ratio of 2.76 × 10 6 . ∙ A dual solvent system is used to change the morphology of the polymer to improve its properties ∙Form better PVA films with a leakage current density of only 5.9 × 10 −7 A/cm [2]@0.5 mV/cm and it is better applied in TFT with a mobility of 8.19 cm 2 V −1 s −1 and a switching ratio of 2.76 × 10 6 ∙The materials used in the whole experiment are environmentally friendly and low-priced

Analysis of Interface Phenomena for High-Performance Dual-Stacked Oxide Thin-Film Transistors via Equivalent Circuit Modeling.

Oxide thin-film transistors (TFTs) have attracted much attention because they can be applied to flexible and large-scaled switching devices. Especially, oxide semiconductors (OSs) have been developed as active layers of TFTs. Among them, indium-gallium-zinc oxide (IGZO) is actively used in the organic light-emitting diode display field. However, despite their superior off-state properties, IGZO TFTs are limited by low field-effect mobility, which critically affects display resolution and power consumption. Herein, we determine new working mechanisms in dual-stacked OS, and based on this, we develop a dual-stacked OS-based TFT with improved performance: high field-effect mobility (∼80 cm2/V·s), ideal threshold voltage near 0 V, high on-off current ratio (>109), and good stability at bias stress. Induced areas are formed at the interface by the band offset: band offset-induced area (BOIA) and BOIA-induced area (BIA). They connect the gate bias-induced area (GBIA) and electrode bias-induced area (EBIA), resulting in high current flow. Equivalent circuit modeling and the transmission line method are also introduced for more precise verification. By verifying current change with gate voltage in the single OS layer, the current flowing direction in the dual-stacked OS is calculated and estimated. This is powerful evidence to understand the conduction mechanism in a dual-stacked OS-based TFT, and it will provide new design rules for high-performance OS-based TFTs.

High-Performance and Radiation-Hardened Solution-Processed ZrLaO Gate Dielectrics for Large-Area Applications.

Radiation hardness is important for electronics operating in harsh radiation environments such as outer space and nuclear energy industries. In this work, radiation-hardened solution-processed ZrLaO thin films are demonstrated. The radiation effects on solution-processed ZrLaO thin films and InOx/ZrLaO thin-film transistors (TFTs) were systemically investigated. The Zr0.9La0.1Oy thin films demonstrated excellent radiation hardness with negligible roughness, composition, electrical property, and bias-stress stability degradation after radiation exposure. The metal-oxide-semiconductor capacitors (MOSCAPs) based on Zr0.9La0.1Oy gate dielectrics exhibited an ultralow flat band-voltage (VFB) sensitivity of 0.11 mV/krad and 0.19 mV/krad under low dose and high dose gamma irradiation conditions, respectively. The low dose condition had a 103 krad (SiO2) total dose and a 0.12 rad/s low dose rate, whereas the high dose condition had a 580 krad total dose and a 278 rad/s high dose rate. Furthermore, InOx/Zr0.9La0.1Oy thin-film transistors (TFTs) exhibited a large Ion/Ioff of 2 × 106, a small subthreshold swing (SS) of 0.11 V/dec, a small interface trap density (Dit) of 1 × 1012 cm-2, and a 0.16 V threshold shift (ΔVTH) under 3600 s positive bias-stress (PBS). InOx/Zr0.9La0.1Oy TFT-based resistor-loaded inverters demonstrated complete swing behavior, a static output gain of 13.3 under 4 V VDD, and an ∼9% radiation-induced degradation. Through separate investigation of the radiation-induced degradation on the semiconductor layer and dielectric layer of TFTs, it was found that radiation exposure mainly generated oxygen vacancies (Vo) and increased electron concentration among gate oxide. Nevertheless, the radiation-induced TFT instability was mainly related to the semiconductor layer degradation, which could be possibly suppressed by back-channel passivation. The demonstrated results indicate that solution-processed ZrLaO is a high-potential candidate for large-area electronics and circuits applied in harsh radiation environments. In addition, the detailed investigation of radiation-induced degradation on solution-processed high-k dielectrics in this work provided clear inspiration for developing novel flexible rad-hard dielectrics.

Enhancement-mode thin film transistor using amorphous phosphorus-doped Indium–Zinc–Tin-Oxide channel layer

In this research, we investigated optical properties of amorphous Phosphorus-doped Indium–Zinc–Tin-Oxide (a-IZTO:P) thin films and their feasibility as the channel layer for thin film transistors (TFTs). The a-IZTO:P TFT with bottom-gate top-contact structure was prepared on silicon substrates by radio frequency (RF) magnetron sputtering at room temperature. After annealing in air at 350 °C, the IZTO:P films kept amorphous and showed good optical transmittance of over 80% within the visible range. The a-IZTO:P TFT operated in enhancement-mode and exhibited promising electrical performance with saturation mobility (μSAT) of 34.6 cm2/V∙s, threshold voltage (VTH) of 0.8 V, subthreshold swing (SS) of 0.53 V/decade and on/off current ratio (ION/IOFF) of 4.88 × 108. In addition, the stability of a-IZTO:P TFTs was also investigated.

Chemically Tunable Organic Dielectric Layer on an Oxide TFT: Poly(p-xylylene) Derivatives.

Inorganic materials such as SiOx and SiNx are commonly used as dielectric layers in thin-film transistors (TFTs), but recent advancements in TFT devices, such as inclusion in flexible electronics, require the development of novel types of dielectric layers. In this study, CVD-deposited poly(p-xylylene) (PPx)-based polymers were evaluated as alternative dielectric layers. CVD-deposited PPx can produce thin, conformal, and pinhole-free polymer layers on various surfaces, including oxides and metals, without interfacial defects. Three types of commercial polymers were successfully deposited on various substrates and exhibited stable dielectric properties under frequency and voltage sweeps. Additionally, TFTs with PPx as a dielectric material and an oxide semiconductor exhibited excellent device performance; a mobility as high as 22.72 cm2/(V s), which is the highest value among organic gate dielectric TFTs, to the best of our knowledge. Because of the low-temperature deposition process and its unprecedented mechanical flexibility, TFTs with CVD-deposited PPx were successfully fabricated on a flexible plastic substrate, exhibiting excellent durability over 10000 bending cycles. Finally, a custom-synthesized functionalized PPx was introduced into top-gated TFTs, demonstrating the possibility for expanding this concept to a wide range of chemistries with tunable gate dielectric layers.