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In this report, we have studied field-effect transistors (FETs) using low-density alumina for electrolytic gating. Device layers have been prepared starting from the structured ITO glasses by printing the In2O3 channels, low-temperature atomic layer deposition (ALD) of alumina (Al2O3), and printing graphene top gates. The transistor performance could be deliberately changed by alternating the ambient humidity; furthermore, ID,ON/ID,OFF-ratios of up to seven orders of magnitude and threshold voltages between 0.66 and 0.43 V, decreasing with an increasing relative humidity between 40% and 90%, could be achieved. In contrast to the common usage of Al2O3 as the dielectric in the FETs, our devices show electrolyte-type gating behavior. This is a result from the formation of protons on the Al2O3 surfaces at higher humidities. Due to the very high local capacitances of the Helmholtz double layers at the channel surfaces, the operation voltage can be as low as 1 V. At low humidities (≤30%), the solid electrolyte dries out and the performance breaks down; however, it can fully reversibly be regained upon a humidity increase. Using ALD-derived alumina as solid electrolyte gating material, thus, allows low-voltage operation and provides a chemically stable gating material while maintaining low process temperatures. However, it has proven to be highly humidity-dependent in its performance. [ABSTRACT FROM AUTHOR]

Printed electronics can benefit from the deployment of electrolytes as gate insulators, which enables a high gate capacitance per unit area (1– 10 μF cm−2) due to the formation of electrical double layers (EDLs). Consequently, electrolyte-gated field-effect transistors (EGFETs) attain high-charge carrier densities already in the subvoltage regime, allowing for low-voltage operation of circuits and systems. This article presents a systematic study of lumped terminal capacitances of printed electrolyte-gated transistors under various dc bias conditions. We perform voltage-dependent impedance measurements and separate extrinsic components from the lumped terminal capacitance. The proposed Meyer-like capacitance model, which also accounts for the nonquasi-static (NQS) effect, agrees well with experimental data. Finally, to verify the model, we implement it in Verilog-A and simulate the transient response of an inverter and a ring oscillator circuit. Simulation results are in good agreement with the measurement data of fabricated devices. [ABSTRACT FROM AUTHOR]

Electrolyte-gated, printed field-effect transistors exhibit high charge carrier densities in the channel and thus high on-currents at low operating voltages, allowing for the low-power operation of such devices. This behavior is due to the high area-specific capacitance of the device, in which the electrolyte takes the role of the dielectric layer of classical architectures. In this paper, we investigate intrinsic double-layer capacitances of ink-jet printed electrolyte-gated inorganic field-effect transistors in both in-plane and top-gate architectures by means of voltage-dependent impedance spectroscopy. By comparison with deembedding structures, we separate the intrinsic properties of the double-layer capacitance at the transistor channel from parasitic effects and deduce accurate estimates for the double-layer capacitance based on an equivalent circuit fitting. Based on these results, we have performed simulations of the electrolyte cutoff frequency as a function of electrolyte and gate resistances, showing that the top-gate architecture has the potential to reach the kilohertz regime with proper optimization of materials and printing process. Our findings additionally enable accurate modeling of the frequency-dependent capacitance of electrolyte/ion gel-gated devices as required in the small-signal analysis in the circuit simulation. [ABSTRACT FROM AUTHOR]

In the domain of printed electronics (PE), field-effect transistors (FETs) with an oxide semiconductor channel are very promising. In particular, the use of high gate-capacitance of the composite solid polymer electrolytes (CSPEs) as a gate-insulator ensures extremely low voltage requirements. Besides high gate capacitance, such CSPEs are proven to be easily printable, stable in air over wide temperature ranges, and possess high ion conductivity. These CSPEs can be sensitive to moisture, especially for high surface-to-volume ratio printed thin films. In this paper, we provide a comprehensive experimental study on the effect of humidity on CSPE-gated single transistors. At the circuit level, the performance of ring oscillators (ROs) has been compared for various humidity conditions. The experimental results of the electrolyte-gated FETs (EGFETs) demonstrate rather comparable currents between 30%–90% humidity levels. However, the shifted transistor parameters lead to a significant performance change of the RO frequency behavior. The study in this paper shows the need of an impermeable encapsulation for the CSPE-gated FETs to ensure identical performance at all humidity conditions. [ABSTRACT FROM AUTHOR]

Printed electronics is a fast-growing emerging technology, which is expected to play a major role in smart sensors for the Internet of Things domain. While there has been considerable progress at the device level by new materials, on circuit level results are still rare. In this letter, we report on the design, simulation, fabrication, and measurement of an inkjet-printed latch, which is an essential building block for digital circuits. Our technology approach is based on electrolyte-gated transistors, which enables low-voltage operation and yields an outstanding electrical performance due to high mobility of the semiconducting, precursor-made In2O3 channel. The fabricated latch can operate reliably down to 0.6 V, where the power consumption is only 16 \mu \textW . The area requirement is about 7 mm2, and in terms of lifetime, no performance degradation was observed during an experimental period of 12 weeks. [ABSTRACT FROM PUBLISHER]

A printed electronics technology has the advantage of additive and extremely low-cost fabrication compared with the conventional silicon technology. Specifically, printed electrolyte-gated field-effect transistors (EGFETs) are attractive for low-cost applications in the Internet-of-Thingsdomain as they can operate at lowsupply voltages. In this paper, we propose an empirical dc model for EGFETs,which can describe the behavior of the EGFETs smoothly and accurately over all regimes. The proposed model, built by extending the Enz--Krummenacher--Vittoz model, can also be used to model process variations,which was not possible previously due to fixed parameters for near threshold regime. It offers a single model for all the operating regions of the transistors with only one equation for the drain current. Additionally, it models the transistors with a less number of parameters but higher accuracy compared with existing techniques. Measurement results from several fabricated EGFETs confirm that the proposed model can predict the I-V more accurately compared with the state-of-the-art models in all operating regions. Additionally, the measurements on the frequency of a fabricated ring oscillator are only 4.7% different from the simulation results based on the proposed model using values for the switching capacitances extracted from measurement data, which showsmore than 2x improvement comparedwith the state-of-the-art model. [ABSTRACT FROM AUTHOR]

Keywords: electrolyte-gated transistors; ink-jet print; ion-gels; ionic liquids; printed electronics The self-assembling ion-gel can be ink-jet printed and therefore enables printing of chemically crosslinked ion-gels. Electrolyte-gated transistors, ink-jet print, ion-gels, ionic liquids, printed electronics. [Extracted from the article]

Electrolyte‐gated transistors (EGTs) represent an interesting alternative to conventional dielectric‐gating to reduce the required high supply voltage for printed electronic applications. Here, a type of ink‐jet printable ion‐gel is introduced and optimized to fabricate a chemically crosslinked ion‐gel by self‐assembled gelation, without additional crosslinking processes, e.g., UV‐curing. For the self‐assembled gelation, poly(vinyl alcohol) and poly(ethylene‐alt‐maleic anhydride) are used as the polymer backbone and chemical crosslinker, respectively, and 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) is utilized as an ionic species to ensure ionic conductivity. The as‐synthesized ion‐gel exhibits an ionic conductivity of ≈5 mS cm−1 and an effective capacitance of 5.4 µF cm−2 at 1 Hz. The ion‐gel is successfully employed in EGTs with an indium oxide (In2O3) channel, which shows on/off‐ratios of up to 1.3 × 106 and a subthreshold swing of 80.62 mV dec−1. [ABSTRACT FROM AUTHOR]