Gate Alignment of Liquid Water Molecules in Electric Double Layer

The behavior of liquid water molecules near an electrified interface is important to many disciplines of science and engineering. In this study, we applied an external gate potential to the silica/water interface via an electrolyte-insulator-semiconductor (EIS) junction to control the surface charging state. Without varying the ionic composition in water, the electrical gating allowed an efficient tuning of the interfacial charge density and field. Using the sum-frequency vibrational spectroscopy, we found a drastic enhancement of interfacial OH vibrational signals at high potential in weakly acidic water, which exceeded that from conventional bulk-silica/water interfaces even in strong basic solutions. Analysis of the spectra indicated that it was due to the alignment of liquid water molecules through the electric double layer, where the screening was weak because of the low ion density. Such a combination of strong field and weak screening demonstrates the unique tuning capability of the EIS scheme, and would allow us to investigate a wealth of phenomena at charged oxide/water interfaces.

Huge magnetoresistance in topological insulator spin-valves at room temperature

Topological insulators (TI) have extremely high potential in spintronic applications. Here, a topological insulators thin-film (TITF) spin valve with the use of the segment gate-controlled potential exhibits a huge magnetoresistance (MR) value higher than 1000% at room temperature which is more than 50 times the MR of typical topological insulators (TI) spin-valves. A high spin-polarized current is provided by the band structure generated by the tunable segment potential. The results reveal a very large resistance difference between the parallel and antiparallel configurations. The MR effect is strongly influenced by the thin-film thickness, the gate potential, the gate size, and the distribution. The proposed results will help to not only improve the room-temperature performance of the spin-valves but also enhance the applications of magnetic memories and spintronic devices.

Controllable potential barrier for multiple negative-differential-transconductance and its application to multi-valued logic computing

Various studies on multi-valued-logic (MVL) computing, which utilizes more than two logic states, have recently been resumed owing to the demand for greater power saving in the current logic technologies. In particular, unlike old-fashioned researches, extensive efforts have been focused on implementing single devices with multiple threshold voltages via a negative-differential current change phenomenon. In this work, we report a multiple negative-differential-transconductance (NDT) phenomenon, which is achieved through the control of partial gate potential and light power/wavelength in a van-der-Waals (vdW) multi-channel phototransistor. The partial gating formed a controllable potential barrier/well in the vdW channel, enabling control over the collection of carriers and eventually inducing the NDT phenomenon. Especially, the strategy shining lights with different powers/wavelengths facilitated the precise NDT control and the realization of the multiple NDT phenomenon. Finally, the usability of this multiple NDT device as a core device of MVL arithmetic circuits such as MVL inverters/NAND/NOR gates is demonstrated.

New single-electron pump regime with highly controllable plateaus

Future quantum based electronic systems will demand robust and highly accurate on-demand sources of current. Generating quantised current has immediate implications for quantum computing, quantum metrology, and electron interferometry. The ultimate limit of quantised current sources is a highly controllable device that manipulates individual electrons. We present a new single-electron pump mechanism, realised in a GaAs two-dimensional electron gas, where electrons are pumped through a one-dimensional split-gate confinement potential rather than more conventionally over a finger-gate potential. This new mechanism yields a new long pumping regime with quantised plateaus that are over two orders of magnitude longer than conventional pumps, and are extremely stable with respect to the applied voltages on the gates. The long plateaus are achieved via the combination of a saddle-point potential profile and enhanced quantum tunnelling, wherein the potential barrier height and shape are modified by the application of a source-drain bias. This new pumping regime cannot be explained by the simple geometrical electrostatic models or back-tunnelling theory that are used to describe conventional single-electron pumps, and we use a simple electrostatic model applied to split-gate confined pumps to explain some of the source-drain bias dependence.

Influence of Common Source and Word Line Electrodes on Program Operation in SuperFlash Memory

A theoretical study of the influence of word line and common source electrodes on the program operation in shrank SuperFlash memory is proposed. Numerical simulations demonstrate that the literature model defined for previous nodes is not always suitable, due to the continuous cell physical size reduction and to the consequent increment of capacitive coupling between the floating gate and adjacent electrodes. To get a deeper insight, an analytical model of the electric field in the region of source side injection is proposed. This model describes the impact of the cell physical and electrical parameters on the vertical and horizontal field components and highlights the strong dependence of the carrier injection on the technology node. Furthermore, the numerical and analytical models estimate the influence of the word line and common source electrodes on the time-to-program, the floating gate potential and the source side injection efficiency, taking into consideration, at the same time, their possible impact on the cell reliability.

Driving Electrolyte-Gated Organic Field-Effect Transistors with Redox Reactions

Organic electrochemical transistors (OECTs) are now well-known, robust and efficient as amplification devices for redox reactions, typically biologically ones. In contrast, electrolyte-gated organic field-effect transistors (EGOFETs) have never been described for that kind of application because field-effect transistors are known as capacitive coupled devices, i.e., driven by changes in capacitance at the electrolyte/gate or electrolyte/semiconductor interface. For such a kind of transistors, any current flowing at the gate electrode is seen as a drawback. However, we demonstrate in this paper that not only the gate potential can trigger the source-drain current of EGOFETs, which is the generally accepted mode of operation, but that the current flowing at the gate can also be used. Because EGOFETs can work directly in water, and as an example of application, we demonstrate the possibility to monitor microalgae photosynthesis through the direct measurement of photosynthetic O2 production within the transistor’s electrolyte, thanks to its electroreduction on the EGOFET’s gate. This paves the way for the use of EGOFETs for environmental monitoring.