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High-entropy alloys (HEAs) or complex concentrated alloys (CCAs) offer a huge research area for new material compositions and potential applications. Since the combination of several elements sometimes leads to unexpected and unpredictable material properties. In addition to the element combinations, the optimization of the element proportions in CCAs and HEAs is also a decisive factor in tailoring desired material properties. However, it is almost impossible to achieve the composition and characterization of CCAs and HEAs with a sufficient number of compositions by conventional experiments. Therefore, an optimized high-throughput magnetron sputtering synthesis to fabricate a new HEA gradient layer of six elements is presented. With this approach, the compositional space of the HEA system CrMoNbTaVW can be studied in different subsections to determine the influence of the individual elements and their combinations on the structure, morphology, and physical properties (hardness and resistivity). It is found that the Cr-, Ta-, and W-rich phases, which have a grain size of 10–11 nm, exhibit the hardest mechanical properties, whereas V-, Ta-, and Cr-rich compounds exhibit the highest electrical resistivity. The combination of high-throughput synthesis, automated analysis tools, and automated data interpretation enables rapid and time-efficient characterization of the novel CrMoNbTaVW gradient film.

Low-frequency noise is a critical characteristic of transistors, but there are only a few experimental works on the noise in printed electronics. In this work, we characterize the low-frequency noise of inkjet-printed electrolyte-gated thin-film transistors (EGTs) with indium-oxide semiconductors. We confirm that the carrier number fluctuation with correlated mobility fluctuation is the dominating noise generation mechanism. Also, we present the benchmark analysis on the noise level of various thin-film technologies. Notably, the extracted value of trap density near the insulator-channel interface is high, indicating an inferior quality of solution-processed and inkjet-printed thin-films. However, because of electrolyte-gating, the large areal gate capacitance compensates the negative effect of the high trap density, effectively reducing the flat-band voltage noise. As a result, the normalized drain current noise is considerably lower than solution-processed transistors and comparable with sputtered inorganic transistors with dielectric gating. This renders the electrolyte-gating approach useful in reducing the noise for printed/solution-based transistors, suitable for low-noise applications.

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, $I_{D,{\mathrm {ON}}}/I_{D,{\mathrm {OFF}}}$ -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.

This paper presents a tiny, flexible, and low-cost all-analog approach for measuring electrodermal activity, based on the conductance of the skin. We propose a tiny, fully-printed system on flexible substrates, which guarantees flexibility and simplifies attachment to the body, and allows for detection of high stress values in form of a binary classification. A major contribution of this paper is the design of the printed hardware, including a novel way to optimize the hardware parameters, which is done via an evolutionary algorithm.

Oxide semiconductors have the potential to increase the performance of inkjet printed microelectronic devices such as field-effect transistors (FETs), due to their high electron mobilities. Typical metal oxides are n-type semiconductors, while p-type oxides, although realizable, exhibit lower carrier mobilities. Therefore, the circuit design based on oxide semiconductors is mostly in n-type logic only. Here we present an inkjet printed pn-diode based on p- and n-type oxide semiconductors. Copper oxide or nickel oxide is used as p-type semiconductor whereas n-type semiconductor is realized with indium oxide. The measurements show that the pn-diodes operate in the voltage window typical for printed electronics and the emission coefficient is 1.505 and 2.199 for the copper oxide based and nickel oxide based pn-diode, respectively. Furthermore, a pn-diode model is developed and integrable into a circuit simulator.

Printed systems spark immense interest in industry, and for several parts such as solar cells or radio frequency identification antennas, printed products are already available on the market. This has led to intense research; however, printed field-effect transistors (FETs) and logics derived thereof still have not been sufficiently developed to be adapted by industry. Among others, one of the reasons for this is the lack of control of the threshold voltage during production. In this work, we show an approach to adjust the threshold voltage (V$_{th}$) in printed electrolyte-gated FETs (EGFETs) with high accuracy by doping indium-oxide semiconducting channels with chromium. Despite high doping concentrations achieved by a wet chemical process during precursor ink preparation, good on/off-ratios of more than five orders of magnitude could be demonstrated. The synthesis process is simple, inexpensive, and easily scalable and leads to depletion-mode EGFETs, which are fully functional at operation potentials below 2 V and allows us to increase V$_{th}$ by approximately 0.5 V.

In this Letter, we report an inkjet-printed resistive switching device based on an Ag/ZnO/Au structure. The device exhibits bipolar resistive switching behavior, a low operation voltage of about 0.7 V, a high on/off ratio of 107, a long retention time exceeding 104 s, and good endurance. The conduction mechanism of the device in low and high resistive states was studied and showed good consistency with the theory of Ohmic and space charge limited conduction mechanisms, respectively.

Silicon (Si) has turned out to be a promising active material for next-generation lithium-ion battery anodes. Nevertheless, the issues known from Si as electrode material (pulverization effects, volume change etc.) are impeding the development of Si anodes to reach market maturity. In this study, we are investigating a possible application of Si anodes in low-power printed electronic applications. Tailored Si inks are produced and the impact of carbon coating on the printability and their electrochemical behavior as printed Si anodes is investigated. The printed Si anodes contain active material loadings that are practical for powering printed electronic devices, like electrolyte gated transistors, and are able to show high capacity retentions. A capacity of 1754 mAh/g$_{Si}$ is achieved for a printed Si anode after 100 cycles. Additionally, the direct applicability of the printed Si anodes is shown by successfully powering an ink-jet printed transistor.

Many different methods, such as screen printing, gravure, flexography, inkjet etc., have been employed to print electronic devices. Depending on the type and performance of the devices, processing is done at low or high temperature using precursor- or particle-based inks. As a result of the processing details, devices can be fabricated on flexible or non-flexible substrates, depending on their temperature stability. Furthermore, in order to reduce the operating voltage, printed devices rely on high-capacitance electrolytes rather than on dielectrics. The printing resolution and speed are two of the major challenging parameters for printed electronics. High-resolution printing produces small-size printed devices and high-integration densities with minimum materials consumption. However, most printing methods have resolutions between 20 and 50 μm. Printing resolutions close to 1 μm have also been achieved with optimized process conditions and better printing technology.

Printed and flexible metal‐oxide transistor technology has recently demonstrated great promise due to its high performance and robust mechanical stability. Herein, fully printed inverter structures using electrolyte‐gated oxide transistors on a flexible polyimide (PI) substrate are discussed in detail. Conductive graphene ink is printed as the passive structures and interconnects. The additive printed transistors on PI substrates show an 𝐼$_{on}$/𝐼$_{off}$ ratio of 10$^{6}$ and show mobilities similar to the state‐of‐the‐art printed transistors on rigid substrates. Printed meander structures of graphene are used as pull‐up resistances in a transistor–resistor logic to create fully printed inverters. The printed and flexible inverters show a signal gain of 3.5 and a propagation delay of 30 ms. These printed inverters are able to withstand a tensile strain of 1.5% following more than 200 cycles of mechanical bending. The stability of the electrical direct current (DC) properties has been observed over a period of 5 weeks. These oxide transistor‐based fully printed inverters are relevant for digital printing methods which could be implemented into roll‐to‐roll processes.

During the past decade to the present time, the topic of printed electronics has gained a lot of attention for their potential use in a number of practical applications, including biosensors, photo...

The gate-away: Chemically cross-linked, adhesive ion-gel is reported. Adhesive ion-gel is synthesized by self-assembled gelation and applied to electrolyte-gated transistors as gate insulators. The adhesive property of ion-gel allows the lamination of gate insulators on semiconductors and electrodes by hand. The adhesive ion-gel exhibits remarkable gating performances in electrolyte-gated transistors.n this study, a facile method to fabricate a cohesive ion-gel based gate insulator for electrolyte-gated transistors is introduced. The adhesive and flexible ion-gel can be laminated easily on the semiconducting channel and electrode manually by hand. The ion-gel is synthesized by a straightforward technique without complex procedures and shows a remarkable ionic conductivity of 4.8 mS cm���1 at room temperature. When used as a gate insulator in electrolyte-gated transistors (EGTs), an on/off current ratio of 2.24��104 and a subthreshold swing of 117 mV dec���1 can be achieved. This performance is roughly equivalent to that of ink drop-casted ion-gels in electrolyte-gated transistors, indicating that the film-attachment method might represent a valuable alternative to ink drop-casting for the fabrication of gate insulators., publishedVersion