A printed vertical field-effect transistor is demonstrated, which decouples critical device dimensions from printing resolution. A printed mesoporous semiconductor layer, sandwiched between vertically stacked drive electrodes, provides <50 nm channel lengths. A polymer-electrolyte-based gate insulator infiltrates the percolating pores of the mesoporous channel to accumulate charge carriers at every semiconductor domain, thereby, resulting in an unprecedented current density of MA cm−2.
Figure 1 a) System comprising the bottom drive electrode along with the printed metal–organic precursor ink that would form the mesoporous semiconductor layer upon annealing. b) After structuring and placing the top drive electrode. c) After the annealing process that removes the polymer and opens the pores; the porous semiconductor channel layer is now sandwiched between the drive electrodes. d) The final vFET geometry after printing the polymer electrolyte (gate dielectric)that covers the porous channel and the displaced gate electrode. e) SEM image showing the actual porous SnO2 surface morphology; the bright white phase represents the material and the dark regions show the pores. f) 3D surface rendering of the reconstructed STEM tomography showing the 3D structure of SnO2. All the images were generated from the sample annealed at 550 °C for 5 min.
Learn more: Tessy. Baby et al., Advanced Materials, 29 (4), 2017, 1603858
A systematic methodology for characterizing ring oscillators in the printed electronics domain is explained. This greatly helps in predicting the switching capacitance and driver capability at each stage, as well as the power consumption of our ink-jet printed ring oscillators. We present inkjet printed circuits which are able to operate at supply voltages as low as ≤2 V. The ink-jet printed inverters show a gain of ∼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 ∼255 Hz and can reach frequencies up to ∼350 Hz at 2 V supply voltage.
Figure 1 Layout of a three stage ring oscillator, fabricated by laser ablation of ITO glass
Figure 2 (a) Output characteristics of a three-stage ring oscillator at a supply voltage VDD of 2 V. (b) Dependency of the frequency f from the supply voltage VDD.
Consequently, the output characteristics as well as the gain of our invertor at a supply voltage of 1V is measured. The maximum gain is 4.4 at an output voltage of 0.55V, which is close to VDD/2. The propoagation delay time was measured to be 2.3 ms.
Learn more: Gabriel C M et al.Appl. Phys. Lett. 111, 102103 (2017); doi: http://dx.doi.org/10.1063/1.4991919
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 E33% 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.
Figure Sketch of the device and in situ measurement principle.
(a) Schematic of the electrochemical tuning cell: a La0.74Sr0.26MnO3 (LSMO) single-crystal thin film (≈13 nm) grown on a SrTiO3 substrate and a high-surface-area carbon cloth serve as working (WE) and counter (CE) electrodes, respectively. The electrodes are separated by an insulating glass fibre (not shown). On application of an external voltage, the ions of the ionic liquid (DEME+-TFSI−) form physical or chemical bonds with the LSMO surface leading to electrostatic (electric-double-layer (EDL) capacitance) or electrochemical (pseudocapacitance (PS)) charge carrier doping, respectively. Both mechanisms allow for manipulating the magnetic state of LSMO. (b) Example of in situ tuning experiment performed at 323 K: the magnetic response (in red) reversibly follows the surface charge modulation (in blue), calculated by integrating the measured current density (in green), on repetitive cycling of the external potential (in black).
Learn more: Alan Molinari et al. Nat Commun. 2017; 8: 15339
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