Unraveling the origin of ferroelectric resistance switching through the interfacial engineering of layered ferroelectric-metal junctions

Ferroelectric memristors have found extensive applications as a type of nonvolatile resistance switching memories in information storage, neuromorphic computing, and image recognition. Their resistance switching mechanisms are phenomenally postulated as the modulation of carrier transport by polarization control over Schottky barriers. However, for over a decade, obtaining direct, comprehensive experimental evidence has remained scarce. Here, we report an approach to experimentally demonstrate the origin of ferroelectric resistance switching using planar van der Waals ferroelectric α-In2Se3 memristors. Through rational interfacial engineering, their initial Schottky barrier heights and polarization screening charges at both terminals can be delicately manipulated. This enables us to find that ferroelectric resistance switching is determined by three independent variables: ferroelectric polarization, Schottky barrier variation, and initial barrier height, as opposed to the generally reported explanation. Inspired by these findings, we demonstrate volatile and nonvolatile ferroelectric memristors with large on/off ratios above 104. Our work can be extended to other planar long-channel and vertical ultrashort-channel ferroelectric memristors to reveal their ferroelectric resistance switching regimes and improve their performances.

Nonlinear Analytical Model of Localized Sub-THz and THz Rectifications in FET Power Detectors

<div>A nonlinear analytical model for THz FET power detectors based on their distributed RC network is presented. This empirical model works well for both drain-unbiased and drain-biased THz FET responses. The physics-based analysis reveals that localized THz rectifications in long channel transistors may be mathematically expressed in the same way as regular RF frequency rectifications of a single lumped device. However, the one lumped FET model can’t work properly at THz frequencies without correct definitions of THz signals on its terminals and independently considers localized rectifications on the source and drain sides. An improved compact one lumped THz FET power detector model with additional Schottky diodes at the source and drain terminals is presented. THz FET detector can also perform a simultaneous self-amplification (active rectification) of the localized THz rectified dc signal when operates in the saturation regime beyond its unity gain frequency. A novel analytical expression for the localized THz dc rectified response is developed for FETs operating in the saturation regime. The presented physics-based model agrees excellently with the measured experimental results of GaAs HEMT transistors at 1.6THz under arbitrary biasing conditions. Many novel electronic designs can be implemented for Millimeter-wave and THz technologies based on the physical FET's nonlinear nature in this frequency range</div>

Nonlinear Analytical Model of Localized Sub-THz and THz Rectifications in FET Power Detectors

<div>A nonlinear analytical model for THz FET power detectors based on their distributed RC network is presented. This empirical model works well for both drain-unbiased and drain-biased THz FET responses. The physics-based analysis reveals that localized THz rectifications in long channel transistors may be mathematically expressed in the same way as regular RF frequency rectifications of a single lumped device. However, the one lumped FET model can’t work properly at THz frequencies without correct definitions of THz signals on its terminals and independently considers localized rectifications on the source and drain sides. An improved compact one lumped THz FET power detector model with additional Schottky diodes at the source and drain terminals is presented. THz FET detector can also perform a simultaneous self-amplification (active rectification) of the localized THz rectified dc signal when operates in the saturation regime beyond its unity gain frequency. A novel analytical expression for the localized THz dc rectified response is developed for FETs operating in the saturation regime. The presented physics-based model agrees excellently with the measured experimental results of GaAs HEMT transistors at 1.6THz under arbitrary biasing conditions. Many novel electronic designs can be implemented for Millimeter-wave and THz technologies based on the physical FET's nonlinear nature in this frequency range</div>

Effect of uniform and non-uniform mesh on the development of turbulent boundary layer

For incompressible flow simulation, it is commonly accepted to use uniform meshes to solve the governing equation of turbulent boundary layer. It follows the laws of conservation stabilizing the flow field in the domain and preventing odd-even decoupling in the pressure field. In this study, Large Eddy Simulation (LES) has been conducted in a long channel. In order to calculate the turbulent boundary layer in the channel, the unsteady Navier-Stokes equations has been adopted at a Reynolds number =180, which is based on mean centerline velocity and the half-width of the channel. The mesh used in this study was based on both stretch and uniform mesh having grid points, which is corresponding to . Turbulence statistics were also calculated to compare to the existing results. In the results, the turbu lent boundary layer was fully developed at around . In addition, fully developed channel flow was achieved at the non-dimensional time of .

Analytical Drain-Current Model and Surface-Potential Calculation for Junctionless Cylindrical Surrounding-Gate MOSFETs

In this paper, we propose an analytical drain-current model for long-channel junctionless (JL) cylindrical surrounding-gate MOSFET (SRG MOSFET). It is based on surface-potential solutions obtained from Poisson’s equation using some approximations and separate conditions. Furthermore, analytical compact expressions of the drain-current have been derived for deep depletion, partial depletion, and accumulation mode. The confrontation of the model with TCAD simulation results, performed with Silvaco Software, proves the validity and the accuracy of the developed model

Seasonal Intermittent Wetlands at the Desaguadero River. Argentine. Past, Present and Future Morphodynamics

The Desaguadero River comprises the upper section of a major hydrological system called Desaguadero-Salado-Chadileuvú-Curacó, located in the central-western sector of Argentina, on the eastern edge of the Diagonal Árida Sudamericana climatic belt. Within this basin, extensive wetlands have developed at the confluence of two main Andean rivers, the Mendoza and San Juan rivers, and from the surface flows generated during floods associated with the mountain ice and snow melts on the catchment area. The water from these rivers was channeled along the Desaguadero river, a north-south approximately 150 km long channel. This paper proposed the Desaguadero river wetlands as a product of co-development of ephemeral lakes and lunettes dunes, based on geomorphological surveying and field work supported by stratigraphical analyses of relict lake-shores and fluvial sedimentary deposits along with historical climatic data. The morphodynamic activity of these wetlands gradually decreased since the end of the 19th century until practically disappeared in the 20th century, due to both natural and anthropic causes.