A simulation study on memory characteristics of InGaZnO-channel ferroelectric-FETs with 2D planar and 3D structure

We have investigated memory characteristics of InGaZnO (IGZO)-channel ferroelectric-FETs (FeFETs) with 2D planar and 3D structure by TCAD simulation to improve the memory window (MW) with a floating-body channel for high-density memory applications. From the study on 2D-planar FeFETs with single-gate (SG) and double-gate (DG), the MW depends on channel length (L) and enhanced with shorter L due to the stronger electrostatic coupling from the source and drain to the center region of the IGZO layer. From the study on 3D-structure FeFETs with macaroni (MAC) and nanowire (NW) structure, the large MW can be obtained especially in NW FeFETs due to the electric-field concentration by Gauss’s law in the 3D electrostatics. Furthermore, we have systematically studied and discussed the device design of MAC and NW structure FeFETs in terms of the diameter and thickness for high-density memory applications. As IGZO thickness decreases and outer diameter of the IGZO layer decreases, the MW increases due to the voltage divider and the electric-field concentration. The device parameters that can maximize the MW can be determined under the constraints of the layout and material based on this study.

Deflection of charged massive particles by a four-dimensional charged Einstein-Gauss-Bonnet black hole

Based on the Jacobi metric method, this paper studies the deflection of a charged massive particle by a novel four-dimensional charged Einstein-Gauss-Bonnet black hole. We focus on the weak field approximation and consider the deflection angle with finite distance effects. To this end, we use a geometric and topological method, which is to apply the Gauss-Bonnet theorem to the Jacobi space to calculate the deflection angle. We find that the deflection angle contains a pure gravitational contribution $\delta_g$, a pure electrostatic $\delta_c$ and a gravitational-electrostatic coupling term $\delta_{gc}$. We find that the deflection angle increases(decreases) if the Gauss-Bonnet coupling constant $\alpha$ is negative(positive). Furthermore, the effects of the BH charge, the particle charge-to-mass ratio and the particle velocity on the deflection angle are analyzed.

Analysis of the charging kinetics in silver nanoparticles-silica nanocomposite dielectrics at different temperatures

Dielectric nanocomposite materials are now involved in a large panel of electrical engineering applications ranging from micro-/nano-electronics to power devices. The performances of all these systems are critically dependent on the evolution of the electrical properties of the dielectric parts, especially under temperature increase. In this study we investigate the impact of a single plane of silver nanoparticles (AgNPs), embedded in a thin silica (SiO2) layer close to the surface, on the electric field distribution, the charge injection and the charge dynamic processes for different AgNPs-based nanocomposites and various temperatures in the range 25°C – 110°C. The electrical charges are injected locally by using an Atomic Force Microscopy (AFM) tip and the related surface potential profile is probed by Kelvin Probe Force Microscopy (KPFM). To get deeper in the understanding of the physical phenomena, the electric field distribution in the AgNPs-based nanocomposites is computed by using a Finite Element Modeling (FEM). The results show a strong electrostatic coupling between the AFM tip and the AgNPs, as well as between the AgNPs when the AgNPs-plane is embedded in the vicinity of the SiO2-layer surface. At low temperature (25°C) the presence of an AgNPs-plane close to the surface, i.e., at a distance of 7 nm, limits the amount of injected charges. Besides, the AgNPs retain the injected charges and prevent from charge lateral spreading after injection. At 110°C the amount of injected charge is increased in the nanocomposites compared to low temperatures. Moreover, the speed of lateral charge spreading is increased for the AgNPs-based nanocomposites. These findings imply that the lateral charge transport is favored in the nanocomposite structures by the closely situated AgNPs because of the strong electrostatic coupling between them.

Multifunctional Polyoxometalate-Platforms for Supramolecular Light-driven Hydrogen Evolution

Multifunctional supramolecular systems are a central research topic in light-driven solar energy conversion. Here, we report a polyoxometalate (POM)-based supramolecular dyad, where two platinum-complex hydrogen evolution catalysts are covalently anchored to an Anderson polyoxomolybdate anion. Supramolecular electrostatic coupling of the system to an iridium photosensitizer enables visible light-driven hydrogen evolution. Combined theory and experiment demon-strate the multifunctionality of the POM, which acts as photosensitizer / catalyst-binding-site and facilitates light-induced charge-transfer and catalytic turnover. Chemical modification of the Pt-catalyst site leads to increased hydrogen evolution reactivity. Mechanistic studies shed light on the role of the individual components and provide a molecular understanding of the interactions which govern stability and reactivity. The system could serve as a blueprint for multifunctional polyoxometalates in energy conversion and storage.

Electrostatic coupling driven dielectric enhancement of PZT/BTO multilayer thin films

In this study, PbZr0.52Ti0.48O3/BaTiO3 (PZT/BTO) multilayers with varying layer fractions were deposited on Pt/Ti/SiO2/Si substrates by sol-gel process. The films were characterized by X-ray diffraction and scanning electron microscopy (SEM). The result shows that there exists a dielectric enhancement when the BTO layer fraction x is around 0.5, and at this fraction, the dielectric constant of PZT/BTO is 590 at 100 kHz, which is far more than that of monolithic PZT or BTO films (478 and 284, respectively). The thermodynamic analysis shows that the measured dielectric constant is close to the simulation values when x closes to 0.5, otherwise it better consists with the series connection calculation values. The result indicates that the internal field resulting from the polarization mismatch between two ferroelectric layers contributes to the enhancement of PZT/BTO heterogeneous thin films.

Theory of Charged Gels: Swelling, Elasticity, and Dynamics

The fundamental attributes of charged hydrogels containing predominantly water and controllable amounts of low molar mass electrolytes are of tremendous significance in biological context and applications in healthcare. However, a rigorous theoretical formulation of gel behavior continues to be a challenge due to the presence of multiple length and time scales in the system which operate simultaneously. Furthermore, chain connectivity, the electrostatic interaction, and the hydrodynamic interaction all lead to long-range interactions. In spite of these complications, considerable progress has been achieved over the past several decades in generating theories of variable complexity. The present review presents an analytically tractable theory by accounting for correlations emerging from topological, electrostatic, and hydrodynamic interactions. Closed-form formulas are derived for charged hydrogels to describe their swelling equilibrium, elastic moduli, and the relationship between microscopic properties such as gel diffusion and macroscopic properties such as elasticity. In addition, electrostatic coupling between charged moieties and their ion clouds, which significantly modifies the elastic diffusion coefficient of gels, and various scaling laws are presented. The theoretical formulas summarized here are useful to adequately capture the essentials of the physics of charged gels and to design new hydrogels with specified elastic and dynamical properties.

An asymmetric mode-localized mass sensor based on the electrostatic coupling of different structural modes with distributed electrodes

Mode-localization sensor with amplitude ratio as output metric has shown excellent potential in the field of micro-mass detection. In this paper, an asymmetric mode -localized mass sensor with a pair of electrostatically coupled resonators of different thickness is proposed. Partially distributed electrodes are introduced to ensure the asymmetric mode coupling of second and third order modes while actuating the thinner resonator by the distributed electrode. The analytical dynamic model is established by Euler–Bernoulli theory and solved by harmonic balance method (HBM) combined with asymptotic numerical method (ANM). Detailed investigations on the linear and nonlinear behavior, critical amplitude as well as the sensitivity of the sensor are performed. The sensitivity of the proposed sensor can be enhanced by about 20 times compared to first order mode-localized mass sensors. Furthermore, by exploiting the nonlinearities while driving the device beyond the critical amplitude for the in-phase mode, the sensor performs a great improvement in sensitivity up to 1.78 times. Besides, the influence of the decrease of coupling voltage is studied, which gives a good reference to avoid mode aliasing.