1,720,984 research outputs found
Accurate Modeling of Amorphous Indium-Gallium-Zinc-Oxide TFTs Deposited on Plastic Foil
No full textAmorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs) are widely used in backplanes of high-definition displays thanks to the high field effect mobility of a-IGZO. To design high-performances and high-functionality a-IGZO circuits accurate physical modeling is required. In this work we propose a physically based analytical model of the drain current of a-IGZO TFTs. Both trapped and free charge are accounted for, and according to many experimental observations the charge transport is described by multiple trapping and release (MTR). The model is compared with both measurements of TFTs fabricated on flexible substrate and numerical simulations, showing negligible error. The resulting mathematical expressions are suitable for computer-aided design implementation and for process characterization
Electrical Characterization of PEDOT:PSS Strips Deposited by Inkjet Printing on Plastic Foil for Sensor Manufacturing
No full textInkjet printing is a viable method for rapid and low-cost manufacturing of flexible sensors. In this paper, we study a technique for inkjet printing of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) strips. A low-cost inkjet desktop printer is used for the fabrication of PEDOT: PSS resistive strips on polyimide substrates. Accounting for several geometries of printed PEDOT: PSS strips, we assess the variability of the fabrication process. Owing to the printing process, we can easily choose the width, length, and thickness. We found that printed strips on polyimide foils show a conductivity equal to 115 S/cm, which linearly increases with the strip thickness. The maximum variability is lower than 13%. The frequency analysis shows a purely resistive impedance in the frequency range investigated (100 Hz-100 kHz). Moreover, the strips folded up to 1000 times shows a resistance variation lower than 6%. The study demonstrates that inkjet printing is a viable method for the simple, fast, reliable, and low-cost fabrication of PEDOT:PSS-based sensors on plastic substrates and circuit interconnections
Operation and modelling of diffusion-driven organic field-effect transistors for high-performance organic electronics
No full textHigh-gain organic transistors are the key building blocks for the development of high-performance organic electronics, including high-sensitivity sensors, signal amplification in sensing systems and large-scale circuits. In this work, we analyze organic transistors based on the diffusion-driven charge-accumulation architecture. This class of organic field-effect transistors maximizes at the same the transconductance and the output resistance. The analysis is based on both electrical measurements and theoretical analysis. The transistor performances are critically compared with that of conventional organic field-effect transistors. A simple analytical model that accounts for the effect of the control drain on the saturation current is developed. The model is included in a circuit simulator and an active-load voltage amplifier with electrically-tunable gain is designed. The gain and bandwidth of the voltage amplifier are suitable for signal conditioning and amplification in organic smart sensors
Split-Gate Ambipolar Thin-Film Transistors and Circuits
No full textSolution-processed ambipolar organic thin-film transistors (TFTs) offer great potential for simple and low-cost fabrication by means of easy-to-fabrication process and both n-type and p-type operation in a single device. Nevertheless, the DC-gain, noise margin, power consumption of ambipolar organic circuits suffer from the fact that always one of the transistors in the inverter cannot be switched off completely. Hence, the typical Z-shaped inerter characteristics is shown in ambipolar inverters. We present novel split-gate ambipolar TFTs architectures (co-planar with gate-gap, non-planar, and inverted non-planar split-gate TFTs) to operate as an either p-type or n-type device depending on the bias voltage at the secondary-gate for complementary circuitry. Non-planar split-gate TFTs with no gate-gap showed orders of magnitude higher performances compared to co-planar split-gate TFTs. We also present 2D numerical simulations for comprehensive understanding of different split-gate device structures. Finally, reconfigurable complementary logic circuits using split-gate were demonstrated for the first time
Physical Modeling of Amorphous InGaZnO Thin-Film Transistors: The Role of Degenerate Conduction
No full textIn amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs), the electron mobility easily exceeds 102/Vs and degenerate band conduction is observed. On the other hand, the field-effect mobility is gate voltage-dependent. Here, we propose a physical model for a-IGZO TFTs accounting for both the non-degenerate and degenerate conductions of trapped and free charges. The comparison between the model and the measurements shows that: 1) the shape of the drain current is almost completely defined by the localized density of states and 2) a transition from non-degenerate-to-degenerate conductions is always observed. This explains the measured gate voltage-dependent field-effect mobility and provides a simple and unified physical picture of the charge transport in a-IGZO TFTs
Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistor using Thermal Annealing
No full textWe present that the hole and electron transport properties in an ambipolar semiconducting polymer can be controlled with thermal annealing. We also show that the split-gate structure offers more accurate characterization for the hole and electron transport parameters such as saturation (μsat.), linear mobility (μlin.), turn- on (Vto), and threshold voltage (Vth) than conventional ambipolar transistor does. As a result, well-balanced hole and electron conduction could be achieved in an ambipolar semiconducting poly-(diketopyrrolopyrrole-terthiophene) (PDPP-3T). It was also observed that hole de-doping (electron doping-like) occurred with thermal annealing, which removed the dipole formation by atmospheric oxygen. Such a recuperation from the atmospherically doped to intrinsically un-doped state changed the characteristics in hole and electron transport, which agreed with the shift in the measured ultraviolet photoelectron spectroscopy (UPS) spectrum. A complementary logic inverter with balanced charging and discharging was demonstrated based on the findings
Analytical Drain Current Model of Both p- and n-Channel OTFTs for Circuit Simulation
No full textOrganic thin-film transistors (OTFTs) are an emerg- ing technology for large scale circuit integration, owing the availability of both p- and n- channel devices. For the technology development and the design of circuits and digital systems, the accurate physical modeling is mandatory. In this work we propose an unified analytical model for both p- and n- type OTFTs. The model is physically based and accounts for a double exponential density of states (DOS). It is simple, symmetric and accurately describes the below-threshold, linear, and saturation regimes via a unique formulation. The model is eventually validated with the measurements of complementary OTFTs fabricated in a fully- printed technology
Analytical Physical-Based Drain-Current Model of Amorphous InGaZnO TFTs Accounting for Both Non-Degenerate and Degenerate Conduction
No full textIn this letter, we propose a physical-based analytical drain current model for amorphous indium–gallium–zinc oxide thin-film transistors (a-IGZO TFTs). As a key feature, the model accounts for both the non-degenerate and the degenerate conduction regimes, including the contributions of trapped and free charges. These two conduction regimes as well as the trapped and free charges are essential to consistently describe a-IGZO TFTs. The model is compared with both exact numerical calculations and measurements. It is continuous, symmetric, simple, and accurate. The model enables to gain physical insight on the material and device properties, and it is a valuable tool for fast process optimization and circuit design
Ultra-sensitive protein detection with organic electrochemical transistors printed on plastic substrates
Full text linkThe detection of protein biomarkers is of great importance in the early diagnosis of severe pathological states. Although in the last decade many approaches to achieve ultra-sensitive protein detection have been developed, most of them require complicated assay set-ups, hindering their adoption in point-of-care applications and on-spot diagnosis. Here we show an organic electrochemical transistor (OECT) biosensor printed on plastic substrates that can selectively detect Immunoglobulin G (IgG) with an unprecedented attomolar detection limit. The OECT is used as a transducer of the biorecognition event taking place at the gate electrode. The measured concentrations are well below the detectable limits of the leading clinical diagnostic enzyme-linked immunosorbent assay, and comparable to the ones gathered with the label-needing single molecule arrays platform. Our work benchmarks the role of plastic OECT-based biosensors as a powerful tool in simple, low cost, yet noninvasive, ultra-sensitive, and widely applicable immunoassay technology
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