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This paper presents a 52 μW heart-rate measurement interface for wearable applications, fabricated on a flexible foil with a-IGZO TFTs. The interface consists of a cascaded diode-connected load preamplifier with a gain of 22 dB in 3 kHz bandwidth. The output is provided as a binary PWM waveform, which can be sent to a reader device using wireless communication. Voltage to pulse-width conversion is achieved with a simple and power minimalistic approach, which exploits a reset integrator. Experimental characterization demonstrates an overall low-frequency gain of the system equal to 25 msec/V and an input referred noise of 186.3 μV rms. In-vivo measurements have been performed, resulting in a 60 bpm heart-rate for a person at rest. © 2018 IEEE.

This work demonstrates the fastest NFC transponder IC with flexible thin-film transistors (TFTs) to be implemented in flexible NFC tags which could be the missing link between the Internet-of-Things and the Internet-of-Everything. The Internet-of-Everything requires low-cost identification and sensor tags, whereby the Silicon-IC could be replaced by lower cost TFT circuits. Our roadmap focuses on thin-film transistor technologies, fabricated directly on plastic film in an industrially upscalable process flow compatible with existing flat panel display (FPD) lines. As a consequence, it is conformal, extreme lightweight and can be placed onto every object. The charge carrier mobility of such transistors is quite low (around 10cm2/Vs), posing big challenges to comply with the different ISO standards set by Si-CMOS-IC.

We present a QVGA (320×240 with 3 sub-pixel) top-emitting AMOLED display with 250ppi resolution using a self-aligned (SA) IGZO TFT backplane on polyimide-foil with full barrier. The back plane process flow is based on a 7 layer photolithography process. The aperture ratio of the top-emitting OLEDs is approx. 80%. An integrated gate driver is shown that can be driven at operation speed equivalent to a 4k2k display at 100Hz.

Our goal is to create thin low-cost flexible NFC tags to allow everyday objects to communicate to smartphones and computers and thus participate in the Internet of Things. We employ amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor circuits processed at low temperatures, less than 250C, directly on thin polyester substrates. Reaching NFC standards with a-IGZO circuits is challenging because the technology is n-type only and the electron mobility (∼15cm7Vs) is lower compared to silicon. As the main result, we show that the most important NFC regulatory standards are met, even with relaxed 5 micron design rules, using optimized design topologies. cop. 2015 IEEE.

A process to make self-aligned top-gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) on polyimide foil is presented. The source/drain (S/D) region's parasitic resistance reduced during the SiN interlayer deposition step. The sheet resistivity of S/D region after exposure to SiN interlayer deposition decreased to 1.5 kΩ/□. TFTs show field-effect mobility of 12.0 cm2/(V.s), sub-threshold slope of 0.5 V/decade, and current ratio (I ON/OFF) of >107. The threshold voltage shifts of the TFTs were 0.5 V in positive (+1.0 MV/cm) bias direction and 1.5 V in negative (-1.0 MV/cm) bias direction after extended stressing time of 104 s. We achieve a stage-delay of ~19.6 ns at V-DD = 20 V measured in a 41-stage ring oscillator. A top-emitting quarter-quarter-video-graphics-array active-matrix organic light-emitting diode display with 85 ppi (pixels per inch) resolution has been realized using only five lithographic mask steps. For operation at 6 V supply voltage (V-DD), the brightness of the display exceeds 150 cd/m2. A process to make self-aligned top-gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) is presented. TFTs show field-effect mobility of 12.0 cm2/(V.s), sub-threshold slope of 0.5 V/decade, and current ratio (I ON/OFF) of over 107. In applications, a 41-stage ring oscillator with a stage-delay of ~19.6 ns (at V-DD = 20 V) and a top-emitting quarter-quarter-video-graphics-array (QQVGA) active-matrix organic light-emitting diode (AMOLED) display with 85 ppi (pixels per inch) resolution using five lithographic mask steps have been realized on a polyimide foil. Copyright 2015 Society for Information Display.

We present a QQVGA (160times120 with 3 sub-pixel) top-emitting AMOLED display with 85ppi resolution using a self-aligned (SA) IGZO TFT backplane on polyimide-foil. The back plane process flow is based on a 5 layer photolithography process. The aperture ratio of the top-emitting OLEDs is approx. 25%. For operation at 6 V supply voltage (VDD), the brightness of the display exceeds 150cd/m2. On the same substrate a 160 stage gate-driver was measured at FHD rate. cop. 2014 Society for Information Display.

AMOLED backplanes were fabricated on both rigid glass and flexible plastic substrates using a solution processed oxide semiconductor processed at temperatures

In this work, we report on high-performance bottom-gate top-contact (BGTC) amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor (TFT) with SiO2 as an etch-stop-layer (ESL) deposited by medium frequency physical vapor deposition (mf-PVD). The TFTs show field-effect mobility (μFE) of 16.0cm2/(V.s), sub-threshold slope (SS -1) of 0.23V/decade and off-currents (IOFF)

AMOLED displays using oxide TFTs and high-quality moisture barrier were fabricated on ultrathin, flexible plastic substrates to give maximum mechanical flexibility. Total display thickness is below 150μm, and repeated rollability at 1 cm roll radius has been demonstrated. Electrical/Mechanical characteristics and reliability of the flexible displays will be presented. cop. 2014 Society for Information Display.

We present an 8b general-purpose microprocessor realized in a hybrid oxide-organic complementary thin-film technology. The n-type transistors are based on a solution-processed n-type metal-oxide semiconductor, and the p-type transistors use an organic semiconductor. As compared to previous work utilizing unipolar logic gates [1], the higher mobility n-type semiconductor and the use of complementary logic allow for a >50x speed improvement. It also adds robustness to the design, which allowed for a more complex and complete standard cell library. The microprocessor consists of two parts, a processor core chip and an instruction generator. The instructions are stored in a Write-Once-Read-Many (WORM) memory formatted by a post-fabrication inkjet printing step, called Print-Programmable Read-Only Memory (P2ROM). The entire processing was performed at temperatures compatible with plastic foil substrates, i.e., at or below 250°C [2]. © 2014 IEEE.

In this study, we report high-quality amorphous indiunrv-galiium-zinc-oxide (a-IGZO) thinfilm transistors (TFTs) fabricated on a polyethylene naphthalate foil using a new back-channel-etch (BCE) process flow. The BCE flow allows a better scalability of TFTs for high-resolution backplanes and related circuits. The maximum processing temperature was limited to less than lôS'C in order to ensure good overiay accuracy (

In this study, the authors report on high-quality amorphous indium-galliunv-zinc oxide thinfilm transistors (TFTs) based on a single-source dual-layer concept processed at temperatures down to ISCC. The dual-layer concept allows the precise control of local charge carrier densities by varying the 02/Ar gas ratio during sputtering for the bottom and top layers. Therefore, extensive annealing steps after the deposition can be avoided. In addition, the dual-layer concept is more robust against variation of the oxygen flow in the deposition chamber. The charge carrier density in the TFT channel is namely adjusted by varying the thickness of the two layers whereby the oxygen concentration during deposition is switched only between no oxygen for the bottom layer and very high concentration for the top layer. The dual-layer TFTs are more stable under bias conditions in comparison with single-layer TFTs processed at low temperatures. Finally, the applicability of this dual-layer concept in logic circuitry such as 19-stage ring oscillators and a TFT backplane on polyethylene naphthalate foil containing a quarter video graphics array active-matrix organic lightemitting diode display demonstrator is proven.

We present a low-temperature metal oxide transistor backplane technology using PECVD dielectrics. We show successful integration of the backplane in flexible 200ppi AMOLED displays on ultrathin polymer films. The displays are encapsulated with a thin-film barrier and the total stack thickness is less than 150μm.

We describe the fabrication and characterization of large-area active-matrix X-ray/photodetector array of high quality using organic photodiodes and organic transistors. All layers with the exception of the electrodes are solution processed. Because it is processed on a very thin plastic substrate of 25 mu;m thickness, the photodetector is only 100 mu;m thick. When combined with an 300-μm-thick X-ray scintillator, this gives a thin, low-weight and shatterproof X-ray detector of ca. 400 mu;m thickness. We demonstrate X-ray imaging under conditions that are used in medical applications. © 2013 Elsevier B.V.

We present a top emitting monochrome AMOLED display with 85dpi resolution using an amorphous Indium-Gallium-Zinc-Oxide (IGZO) TFT backplane on PEN-foil. Maximum processing temperature was limited to 150 °C in order to ensure an overlay accuracy < 3μm on PEN foil. The backplane process flow is based on a 7 mask photolithography process that yields a final mobility of the IGZO TFTs of ∼ 13 cm2A/s.

Organic transistor parameters (i.e. threshold, stability, on/off current ratio, subthreshold slope) are not only defined by the organic semiconductor (OSC) itself, but they strongly depend on the interface between the OSC and the gate insulator (GI), the interface between the metal electrodes (source and drain) and the OSC, as well as on the transistor structure (i.e. coplanar or staggered). Since in Organic Thin-Film Transistors (OTFTs) the charge transport takes place very close to the GI/OSC interface [1], the interaction between the insulator and the semiconductor plays an important role in determining the transistor performance [2-4]. In this work, we provide a quantitative analysis of the interaction between the gate insulator and the organic semiconductor. OTFTs made with different structures, gate insulators, organic semiconductors, and fabrication processes are considered.

We present a QQVGA top emitting monochrome AMOLED display with 85dpi resolution using an organic TFT backplane on low temperature PEN-foil. The back plane process flow is based on a 7 layer photolithography process that yields a final mobility of the OTFT of ∼0.4cm2/Vs. The aperture ratio of the top-emitting OLEDs is over 75%. For operation at 10 V supply voltage (VDD), the brightness of the display using red, green or blue OLEDs exceeds 200cd/m2. We will furthermore discuss the relevant parameters that determine the performance of our organic backplanes for OLED displays, in particular bias stress, output resistance, uniformity and current drive capability.

In this chapter, fully integrated organic RFID tags are demonstrated. These tags are inductively-coupled at a base frequency of 13.56 MHz and can be read out at distances up to 10 cm, which is the expected readout distance for proximity readers. We also demonstrate next generation transponder chips, fabricated in a dual-gate technology. The additional gate, backgate, is used to control the threshold voltage and allows integration into more robust unipolar, dual-VT transponder chips. Finally, we realized an 8-bit transponder chip having data rates that are EPC-compatible. This has been achieved in our thin-film transistor technology by introducing a high-k Al2O 3 gate dielectric, by scaling the channel lengths down to 2 mm and by reducing the overlap capacitance of the parasitic source-gate and drain-gate capacitors. © 2011 Springer Science+Business Media B.V.

The first dual-gate thin-film transistor (DGTFT) was reported in 1981 with CdSe as the semiconductor. Other TFT technologies such as a-Si:H and organic semiconductors have led to additional ways of making DGTFTs. DGTFTs contain a second gate dielectric with a second gate positioned opposite of the first gate. The main advantage is that the threshold voltage can be set as a function of the applied second gate bias. The shift depends on the ratio of the capacitances of the two gate dielectrics. Here we review the fast growing field of DGTFTs. We summarize the reported operational mechanisms, and the application in logic gates and integrated circuits. The second emerging application of DGTFTs is sensitivity enhancement of existing ion-sensitive field-effect transistors (ISFET). The reported sensing mechanism is discussed and an outlook is presented. Dual-gate thin-film transistors (DGTFTs) have gained popularity in recent years. The additional second gate allows controlled shifting of the threshold voltage. The shift depends on the ratio of the capacitances of the two gate dielectrics. We summarize the reported operation mechanism and review the application of DGTFTs in both integrated circuits and sensors. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We demonstrate high performance X-ray imaging detectors on foil suitable for medical grade X-ray imaging applications. The detectors are based on solution-processed organic photodiodes forming bulk-heterojunctions from photovoltaic donor and acceptor blend. The organic photodiodes are deposited using an industrially compatible slot die coating technique with end of line processing temperature below 100° C. These photodiodes have extremely low dark leakage current density of 10-7 mA/cm2 at -2V bias with very high yield and have peak absorption around 550 nm wavelength. We combine these organic photodiodes with high mobility metal oxide semiconductor based thin film transistor arrays with high pixel resolution of 200ppi on thin plastic substrate. When combined with a typical CsI(TI) scintillator material on top, they are well suited for low dose X-ray imaging applications. The optical crosstalk is insignificant upto resolution of 200 ppi despite the fact that the photodiode layer is one continuous layer and is non-pixelated. Low processing temperatures are another key advantage since they can be fabricated on plastic substrate. This implies that we can make X-ray detectors on flexible foil. Those detectors can be mechanically more robust and light weight when compared to amorphous Si based detectors fabricated on glass substrate.

Recently, complex circuits of organic thin-film transistors have been shown. The use of complementary logic can significantly ease the design of large integrated circuits. However, the performance of complementary logic in organic thin-film technology has not been able to equivale that of unipolar logic, due to the difficulty to densely integrate and simultaneously optimize p-type and n-type transistors on a single substrate. Here, we develop an optimized complementary process for C60 n-type and pentacene p-type transistors, both having bottom-gate bottom-contact geometry. Using this complementary technology, we show ring-oscillators with a stage-delay below 1 μs at a supply-voltage of 20 V. © 2010 American Institute of Physics.

Motivation: Electronics based on organic thin-film transistors (OTFTs) enables a variety of attractive applications like active matrix displays, flexible sensor systems and, at a longer timescale, printable item-level RFID tags. As analogue circuit applications of OTFTs are being extensively researched, accurate OTFT models suitable for the simulation of these circuits become increasingly more relevant and urgent. In this work we propose a physically-based, analytical model for OTFTs, which takes into account the influence of both tail and deep localized states. The model is symmetric, considers channel modulation, and provides good accuracy both in sub-threshold and above-threshold regime. It also preserves the continuity of the small-signal parameters, as it is required for analogue simulations. Model, results and discussion: Charge transport in organic semiconductors is usually explained by means of the variable range hopping (VRH) theory, i.e., thermally activated tunnelling of carriers between localized states. From a percolation model of hopping between localized states, Vissenberg and Matters [1] developed an analytic expression of field-effect mobility used to describe transport in OTFTs. Their model is based on the assumption of an exponential DOS. From the direct determination of the DOS by high lateral resolution Kelvin probe measurements [2], it was shown that the ‘’real’’ DOS is well fitted by a Gaussian function in tail states and an exponential function in deep states. Therefore the Vissenberg and Matters work is a very good approximation of the Gaussian DOS only in tail states [3] whereas it neglects deep states. Based on these experimental evidences, we consider the influence of both tail and deep states on the OTFT current. We show that the former are important at high gate voltages when the transistor works in strong accumulation regime and the latter are relevant at low VGS, both in saturation and in sub-threshold regime (see Fig. 1). Channel length modulation is also accounted for in the model, ensuring both current and output-resistance continuity at the pinch-off voltage: this is very important when the model is used in a CAD environment and for analogue design purposes. In Figs. 1, 2 the proposed model (red continuous line) is compared with experimental data: accuracy is good both below- and above- threshold. The model is fully symmetrical and can be easily extended to take into account contact resistance effects. The model parameters are extracted in a simple and direct way from the experimental measurements (without any optimization method) using the standard procedure described in [4]. From measurement in biasing conditions where the drain current is dominated by deep-states, one can determine the flat-band voltage VFB, the conductivity sd and the DOS characteristic temperature Td. It is worth noting that the flat-band condition is unambiguously determined from the deep-states current and, contrary to [5], no other threshold voltage needs to be introduced. Measurements where ID is dominated by tail-states current give st and Tt. Apart from geometric parameters, the model requires only five physical parameters related to the material properties.

(Figure Presented) Controlling the morphology of soluble small molecule organic semiconductors is crucial for the application of such materials in electronic devices. Using a simple dip-coating process we systematically vary the film drying speed to produce a range of morphologies, including oriented needle-like crystals. Structural characterization as well as electrical transistor measurements show that intermediate drying velocities produce the most uniformly aligned films. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

A target application for plastic RFID tags is Electronic Product Coding (EPC). The EPC-specifications set some demanding requirements for RFID tags. In this work, we review the work that has been done to fulfill some of these specifications. We describe a complete 64-bit RFID tag that is inductively-coupled at a base carrier frequency of 13.56 MHz, and transmits data at rates below 1 kb/s. Next, we demonstrate 8-bit RFID transponder chips having data rates of 50 kb/s, an important milestone for organic RFID tags in view of EPC specifications. ©The Electrochemical Society.