Hybrid supercapacitors for reversible control of magnetism

Electric field tuning of magnetism is one of the most intensely pursued research topics of recent times aiming at the development of new-generation low-power spintronics and microelectronics. However, a reversible magnetoelectric effect with an on/off ratio suitable for easy and precise device operation is yet to be achieved. Here we propose a novel route to robustly tune magnetism via the charging/discharging processes of hybrid supercapacitors, which involve electrostatic (electric-double-layer capacitance) and electrochemical (pseudocapacitance) doping. We use both charging mechanisms—occurring at the La0.74Sr0.26MnO3/ionic liquid interface to control the balance between ferromagnetic and non-ferromagnetic phases of La1−xSrxMnO3 to an unprecedented extent. A magnetic modulation of up to ≈33% is reached above room temperature when applying an external potential of only about 2.0 V. Our case study intends to draw attention to new, reversible physico-chemical phenomena in the rather unexplored area of magnetoelectric supercapacitors

Digital power and performance analysis of inkjet printed ring oscillators based on electrolyte-gated oxide electronics

Printed electronic components offer certain technological advantages over their silicon based counterparts, like mechanical flexibility, low process temperatures, maskless and additive manufacturing possibilities. However, to be compatible to the fields of smart sensors, Internet of Things, and wearables, it is essential that devices operate at small supply voltages. In printed electronics, mostly silicon dioxide or organic dielectrics with low dielectric constants have been used as gate isolators, which in turn have resulted in high power transistors operable only at tens of volts. Here, we present inkjet printed circuits which are able to operate at supply voltages as low as <= 2 V. Our transistor technology is based on lithographically patterned drive electrodes, the dimensions of which are carefully kept well within the printing resolutions; the oxide semiconductor, the electrolytic insulator and the top-gate electrodes have been inkjet printed. Our inverters show a gain of similar to 4 and 2.3 ms propagation delay time at 1 V supply voltage. Subsequently built 3-stage ring oscillators start to oscillate at a supply voltage of only 0.6 V with a frequency of similar to 255 Hz and can reach frequencies up to similar to 350 Hz at 2 V supply voltage. Furthermore, we have introduced a systematic methodology for characterizing ring oscillators in the printed electronics domain, which has been largely missing. Benefiting from this procedure, we are now able to predict the switching capacitance and driver capability at each stage, as well as the power consumption of our inkjet printed ring oscillators. These achievements will be essential for analyzing the performance and power characteristics of future inkjet printed digital circuits

Inkjet Printed, High Mobility Inorganic-Oxide Field Effect Transistors Processed at Room Temperature

Printed electronics (PE) represents any electronic devices, components or circuits that can be processed using modern-day printing techniques. Field-effect transistors (FETs) and logics are being printed with intended applications requiring simple circuitry on large, flexible (e.g., polymer) substrates for low-cost and disposable electronics. Although organic materials have commonly been chosen for their easy printability and low temperature processability, high quality inorganic oxide-semiconductors are also being considered recently. The intrinsic mobility of the inorganic semiconductors are always by far superior than the organic ones; however, the commonly expressed reservations against the inorganic-based printed electronics are due to major issues, such as high processing temperatures and their incompatibility with solution-processing. Here we show a possibility to circumvent these difficulties and demonstrate a room-temperature processed and inkjet printed inorganic-oxide FET where the transistor channel is composed of an interconnected nanoparticle network and a solid polymer electrolyte serves as the dielectric. Even an extremely conservative estimation of the field-effect mobility of such a device yields a value of 0.8 cm2/(V s), which is still exceptionally large for a room temperature processed and printed transistor from inorganic materials

Bulk Nanostructured Materials: Non-Mechanical Synthesis

An overview of the synthesis and processing techniques for bulk nanostructured materials that are based on ‘‘bottom-up’’ approaches is presented. Typically, these processes use nanoparticles, which can be produced by a variety of methods in the gas, liquid or solid state, as the basic building blocks. Their assembly into bulk nanostructured materials requires at least one more processing step, such as compaction or the formation of thick films. For certain nanostructures, film deposition techniques can also be employed. A wide range of nanostructures – from thick films with theoretical density to bulk nanocrystalline materials with nanoporosity – exhibiting novel structural and functional properties useful in many fields of applications are presented. Additionally, the properties of these bulk nanostructured materials can be categorized as either tailored, i.e., microstructure-dependent and inherently irreversible, or tunable, i.e., reversible by the application of an external field. Examples of both categories of properties are presented and the special role of the synthesis and processing routes to achieve the necessary nanostructures is emphasized

High-Speed, Low-Voltage, and Environmentally Stable Operation of Electrochemically Gated Zinc Oxide Nanowire Field-Effect Transistors

Single-crystal, 1D nanostructures are well known for their high mobility electronic transport properties. Oxide-nanowire field-effect transistors (FETs) offer both high optical transparency and large mechanical conformability which are essential for flexible and transparent display applications. Whereas the “on-currents” achieved with nanowire channel transistors are already sufficient to drive active matrix organic light emitting diode (AMOLED) displays; it is shown here that incorporation of electrochemical-gating (EG) to nanowire electronics reduces the operation voltage to ≤2 V. This opens up new possibilities of realizing flexible, portable, transparent displays that are powered by thin film batteries. A composite solid polymer electrolyte (CSPE) is used to obtain all-solid-state FETs with outstanding performance; the field-effect mobility, on/off current ratio, transconductance, and subthreshold slope of a typical ZnO single-nanowire transistor are 62 cm2/Vs, 107, 155 μS/μm and 115 mV/dec, respectively. Practical use of such electrochemically-gated field-effect transistor (EG FET) devices is supported by their long-term stability in air. Moreover, due to the good conductivity (≈10−2 S/cm) of the CSPE, sufficiently high switching speed of such EG FETs is attainable; a cut-off frequency in excess of 100 kHz is measured for in-plane FETs with large gate-channel distance of >10 μm. Consequently, operation speeds above MHz can be envisaged for top-gate transistor geometries with insulator thicknesses of a few hundreds of nanometers. The solid polymer electrolyte developed in this study has great potential in future device fabrication using all-solution processed and high throughput techniques

Engineering a 3D MoS2 foam using keratin exfoliated nanosheets

Owing to their exceptional optical and electronic properties; two-dimensional transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) have attracted immense research interest. However, the lack of an efficient route for large-scale production of nano-layered sheets with long shelf-life and colloidal stability to avoid their restacking upon drying poses a significant bottleneck in their widespread use limiting their utility in device fabrication especially in functional electronics. Here, we report a facile method to obtain the high-quality dispersion of nano-layered MoS2 nanosheets with exceptionally high yield of similar to 56%, long shelf life and excellent electronic properties, which was confirmed by the high conductivity values of 5 x 10(-4) S cm(-1) (much higher than the best reports) measured on the as-casted film. Moreover, we subsequently show that the exfoliated material can be transformed into a 3D MoS2 foam with intact optical properties confirmed from the presence of the band gap at similar to 2.1 eV, and photothermal behavior showing the increase of similar to 40 degrees C within 2 min of NIR irradiation making this material an attractive substrate for applications in catalysis, sensing and functional electronics