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Effect of space charge limited current on performance of organic field-effect transistors
摘要： The crucial parameter that determines the performance of a semiconductor material in organic field-effect transistors (OFETs) is the charge carrier mobility. The conventional method of its determination based on Shockley’s equations can lead to incorrect mobility evaluation due to contact effects. Particularly, in the common staggered OFET architecture (top-contact bottom-gate or bottom-contact top-gate), the space-charge limited current (SCLC) effect in the active layer under/above the source and drain contacts decreases the source-drain current. In this work, we model the effect of SCLC under/above the source and drain electrodes on the OFET apparent mobility (i.e., calculated from the device characteristics) and apparent threshold voltage for different active layer thickness and intrinsic mobility anisotropy. For the saturation regime, we derived simple analytical expressions for transfer characteristics and apparent mobility. Our modeling shows that the apparent OFET mobility is more than five times lower than the intrinsic one for the active layer thicker than 100 nm with mobility anisotropy (along vs across the active layer) higher than 100. While the SCLC effect does not change the apparent threshold voltage, it reveals itself as a kink at near zero voltage in the output characteristics. The proposed model gives analytical expressions for the transfer characteristics and apparent mobility as explicit functions of the intrinsic mobility and the device parameters in the saturation regime and as implicit functions in the linear regime. Our findings provide guidelines for accurate evaluation of the intrinsic mobility in OFETs fabricated in the staggered architecture and for further improvement of OFET performance.
关键词： Organic field-effect transistors,Organic thin-film transistors,Space charge limited current,Contact effects,Modeling
更新于2025-09-11 14:15:04
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Sol-Gel Derived Dip Coated ZnO – La <sub/>2</sub> O <sub/>3</sub> Thin Film Transistors
摘要： ZnO thin ?lms are fabricated utilizing a cost effective sol-gel dip coating technique and potentially applied as active material in thin ?lm transistors (TFT). The channel length of the TFT is maintained at 40 μm. Thermally deposited high –k La2O3 is used as dielectric material. The fabricated ZnO ?lms are annealed in oxygen atmosphere at 500?C for 1 hour and characterized by XRD, EDX and SEM analysis. The TFTs are fabricated in top gate coplanar electrodes structure on glass substrates. The electrical characteristics of the TFTs are investigated and some important electrical parameters are evaluated. The TFTs exhibit ?eld effect mobility of 1.9 cm2/VS, low threshold voltage of 2.5 Volt, high ON/OFF current ratio of 107, sub-threshold swing of 0.8V/decade, transconductace of 1.2 × 10?3 mho and gain band-width product of 20 kHz.
关键词： ZnO,sol-gel dip coating,thin film transistors,electrical characteristics,La2O3
更新于2025-09-11 14:15:04
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Optical properties of selenium sulfide thin film produced via chemical dropping method
摘要： This paper describes the production of selenium sulfide (SeS2) crystalline thin film on commercial glass substrates, via chemical bath deposition. Transmittance, absorption, dielectric constant and refractive index of the produced films were investigated by UV/VIS Spectrum. It was found that changes occurred on the characteristics of the films and they were determined as a function of selenium sulfide concentration, which varied between 2 × 10?3 and 5 × 10?3 M. The structure of the film was analyzed using FTIR spectrum. The calculated refractive index values fell between 1.5 and 1.6, whereas the transmission ratio of the films was around 80–90%. Moreover, a peak in the reflectance was observed at 320–330 nm for all investigated samples. The highest dielectric constant for the films was obtained at the deposition concentration of 0.005 M. This study is believed to be useful for thin film production.
关键词： Selenium sulfide,Thin film,Chemical dropping,Organic thin film,SeS2 thin films
更新于2025-09-10 09:29:36
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New Advances in Hydrogenation Processes - Fundamentals and Applications || Hydrogenation of Polycrystalline Silicon Thin‐Film Transistors
摘要： In this chapter, the behavior of hydrogen (H) atoms in polycrystalline silicon (poly‐Si) thin film is investigated in detail in order to evaluate and improve the quality of hydrogenated poly‐Si thin films. Hydrogenation drastically improves the Hall effect mobility, whereas excessive hydrogenation tends to degrade it. The catalytic method is useful to inhibit excessive hydrogenation and damage suffered by the electric‐field acceleration of charged particle. The H‐termination of the dangling bonds at grain boundaries can be observed indirectly or directly by chemical etching and Raman microscopy. This H‐termination appeared as the 2000?cm‐1 local vibrational mode (LVM) in Raman spectra. The breaking of the Si–Si bonds by hydrogenation was detected as the 2100?cm‐1 LVM. In addition, the defects generated in the plasma process exhibit multiple fine LVMs after hydrogenation. Moreover, we investigated the hydrogenation of low‐temperature (LT) poly‐Si thin‐film transistors (TFTs) from the perspective of the gettering phenomenon. The most important parameter for effective hydrogenation using H gas annealing is the rate of cooling from 400°C.
关键词： Raman scattering,hydrogenation,thin film,polycrystalline silicon,thin‐film transistors
更新于2025-09-10 09:29:36
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Synthesis of Mesoporous TiO2/Boron-Doped Diamond Photocatalyst and Its Photocatalytic Activity under Deep UV Light (λ = 222 nm) Irradiation
摘要： There is a need for highly efficient photocatalysts, particularly for water purification. In this study, we fabricated a mesoporous TiO2 thin film on a boron-doped diamond (BDD) layer by a surfactant-assisted sol-gel method, in which self-assembled amphiphilic surfactant micelles were used as an organic template. Scanning electron microscopy revealed uniform mesopores, approximately 20 nm in diameter, that were hexagonally packed in the TiO2 thin film. Wide-angle X-ray diffraction and Raman spectroscopy clarified that the framework crystallized in the anatase phase. Current–voltage (I–V) measurements showed rectification features at the TiO2/BDD heterojunction, confirming that a p–n hetero-interface formed. The as-synthesized mesoporous TiO2/BDD worked well as a photocatalyst, even with a small volume of TiO2 (15 mm × 15 mm × c.a. 1.5 μm in thickness). The use of deep UV light (λ = 222 nm) as a light source was necessary to enhance photocatalytic activity, due to photo-excitation occurring in both BDD and TiO2.
关键词： photocatalyst,water purification,thin film,surfactant-assisted sol-gel method,p-n heterojunction,deep UV light,mesoporous metal oxide
更新于2025-09-10 09:29:36
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V2O5 Thin Films as Nitrogen Dioxide Sensors ?
摘要： Vanadium pentoxide thin films were deposited onto insulating support by means of rf reactive sputtering from a metallic vanadium target. Argon-oxygen gas mixtures of different compositions controlled by the flow rates were used for sputtering. X-ray diffraction at glancing incidence (GIXD) and Scanning Electronic Microscopy (SEM) were used for structural and phase characterization. Thickness of the films was determined by the profilometry. It has been confirmed by GIXD that the deposited films are composed of V2O5 phase. The gas sensing properties of V2O5 thin films were investigated at temperatures from range 410–617 K upon NO2 gas of 4–20 ppm. The investigated material exhibited good response and reversibility towards nitrogen dioxide. The effect of metal-insulator transition (MIT) on sensor performance has been observed and discussed for the first time. It was found that a considerable increase of the sensor sensitivity occured above 545 K, which is related to postulated metal-insulator transition.
关键词： reactive sputtering,vanadium pentoxide,metal-insulator transition (MIT),electrical properties,thin film,gas sensor,nitrogen dioxide
更新于2025-09-10 09:29:36
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Thermal oxidation effects on physical properties of CuO<sub>2</sub> thin films for optoelectronic application
摘要： In this research, high quality copper dioxide (Cu2O) and copper oxide (CuO) thin films have been prepared using RF sputtering method under ranges of annealing temperatures. The results showed that high transparent samples along with the transparency values increases from 48% to 68%. At low annealing temperature, however, optical properties drops sharply. It has been found that the value of energy band-gap were 2.35eV – 2.62eV as the annealing temperature increases. Further, SEM and X-Ray Diffraction techniques were used to measure and investigate the surface morphology and the homogeneity of Cu2O and CuO thin films, respectively.
关键词： Annealing temperature,Sol RF sputtering.,copper dioxide,thin film
更新于2025-09-10 09:29:36
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Assessment of thin-film photocatalysis inactivation of different bacterial indicators and effect on their antibiotic resistance profile
摘要： The presence of bacterial pathogens in water bodies, alongside their growing antibiotic resistance, endanger access to freshwater sources and necessitate their successful inactivation with a proper disinfection technology. In the present study, a parallel plate reactor (PPL) with immobilized photocatalyst was used as a disinfection system for the inactivation of two bacterial indicators (Escherichia coli and Enterococcus faecalis) in aqueous samples. Experiments were carried out at parallel plate reactor configuration (PPL) operated in recycling batch mode. Titanium Tetraisopropoxide (TTIP) based thin-film coated photocatalyst surfaces were used and assessed operations parameters were; pH, initial bacteria concentration, source and type of bacteria. The effect of the photocatalytic process on antibiotic resistance profile of target bacteria was also investigated as it may serve as a pioneering step in the field of well-established and modern disinfection method development, without causing proliferation of antibiotic resistance. The observed courses of bacterial inactivation and the final disinfection rates point out diversity in the level of interaction between different type/source of bacteria and photocatalyst of concern. According to the results, a stationary phase of bacteria inactivation proceeded with a rapid and efficient one for the case of E. faecalis (99% removal after 180 min and 99.9% removal after 240 min), while the trend for E. coli is more likely to be described as extended along the process time. Among the tested antibiotics, E. coli Minimum inhibition concentration (MIC) values for beta-lactam, macrolide and aminoglycoside groups were considerably altered (namely Ampicillin, Cefaclor, Clarithromycin - Erythromycin and Amikacin, respectively). PC oxidation was approved to be efficient on bacterial inactivation and trigger alterations on resistance behaviour of E.coli and Enterococcus sp. strains.
关键词： Photocatalysis,Parallel Plate Reactor,Minimum inhibitory concentration (MIC),E. coli,Antibiotic resistance,Inactivation,Thin-Film,E. faecalis
更新于2025-09-10 09:29:36
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Uniform Insulating Properties of Low-Temperature Curable Gate Dielectric for Organic Thin-Film Transistor Arrays on Plastic Substrate
摘要： Achieving a high-resolution display on a plastic substrate requires a to ensure dimensional stability during fabrication process, including the deposition of gate dielectrics. Evaluation platform to confirm the uniform insulating properties of organic dielectric material prior to actual application to organic thin-film transistor (OTFT) arrays was proposed. This test method enabled verification of the suitability of the low-temperature curable dielectric and chemical resistance during fabrication process. A cross-linked poly(hydroxy imide) (PHI) that can be cured at a low temperature of 130°C exhibited stable insulating properties in a large area that sudden breakdown was not observed in an electric field up to 4 MV/cm. Thiophene-thiazole-based copolymer semiconductor was used as an active layer and inkjet-printed. In all the processes, the temperature of the substrate was kept below 130°C, and 4.8-inch electrophoretic display panels on a polyethylene naphthalate (PEN) substrate with a resolution of 98 dpi was demonstrated.
关键词： Organic thin-film transistors,Organic gate dielectric,Plastic substrates,Low-temperature process,Polymer semiconductor,Flexible displays,Inkjet printing
更新于2025-09-10 09:29:36
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[IEEE 48th European Solid-State Device Research Conference (ESSDERC 2018) - Dresden (2018.9.3-2018.9.6)] 2018 48th European Solid-State Device Research Conference (ESSDERC) - Low Temperature and Radiation Stability of Flexible IGZO TFTs and their Suitability for Space Applications
摘要： In this paper, Low Earth Orbit radiation and temperature conditions are mimicked to investigate the suitability of flexible Indium-Gallium-Zinc-Oxide transistors for lightweight space-wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive sensors such as radiation detectors or physiological monitors. Due to the harsh environment to which these space-wearables would be exposed, they have to be able to withstand high radiation doses and low temperatures. For this reason, the impacts of high energetic electron irradiation with fluences up to 1012 e-/cm2 and low operating temperatures down to 78 K, are investigated. This simulates 278 h in a Low Earth Orbit. The threshold voltage and mobility of transistors that were exposed to e- irradiation are found to shift by +0.09 ± 0.05V and -0.6 ± 0.5cm2 V-1 s-1. Subsequent low temperature exposure resulted in additional shifts of +0.38 V and -5.95 cm2 V-1 s-1 for the same parameters. These values are larger than the ones obtained from non-irradiated reference samples. If this is considered during the systems’ design, these devices can be used to unobtrusively integrate sensor systems into space-suits.
关键词： amorphous oxides,flexible electronics,thin film transistors,wearables,space applications
更新于2025-09-10 09:29:36