Summertime turbulent heat fluxes at East Antarctica over neighbouring rocky and ice shelf sites

During the ninth Indian Scientific Expedition to Antarctica, in the year 1990, a micro-meteorological tower was installed at Maitri (70° S, 12° E) on the rocky terrain and on an experimental basis, on the nearby ice-shelf at the location of Dakshin Gangotri (70° 7¢ S, 11° 7¢ E). The synoptic features strongly influencing over the sites are the southeasterly katabatic winds from the polar cap and/or northerly low level warm and humid winds from the sea. These flows are responsible for the formation of strong surface based inversion and strong convective conditions at the ice shelf and rocky terrain during the minimum and maximum insolation periods, respectively. This paper presents a study of surface layer structure over two contrasting surfaces on near-coastal Antarctica and deals with the significance of the energy exchange processes over the rocky Antarctic region and the parameterization of turbulent fluxes over surfaces having strong inversion/convection conditions. The paper makes use of turbulence structure functions which are different from the conventional one given by Panofsky and Dutton (1984).

Simulation of the characteristics of low-voltage gates on combined cylindrical surrounding gate field-effect nanotransistors

The applicability of the architecture of a nanoscale surrounding gate field-effect transistor with a combined cylindrical working area for low-voltage applications is discussed. At the same time, the licensed TCAD Sentaurus instrument and technological modeling system is used as a tool. The transistor architecture under consideration involves combining the working zones of n-channel and p-channel transistors with one common gate. At the same time, the efficiency of suppressing short-channel effects is maintained and a high level of transistor current is provided in the strong inversion mode. Based on this architecture, a TCAD model of the NAND gate has been developed, the design of which contains two independent surrounding gates one combined working area. The use of the proposed gate architecture makes it possible to reduce the number of required transistor structures per gate by three times. This leads to a decrease in the switched capacity and power dissipation. From the simulation results, the gate geometric parameters with a working area length of 25 nm and a diameter of 8.5 nm, which can function at control voltages of 0.5 V in the frequency range up to 20 GHz with high gain, are determined. The switching time delay is 0.81 ps. The TCAD model of a half-adder is developed in the basis 2NAND. According to the simulation results, the efficiency of the prototype, which performs binary code addition operations with a delay of 4.2 ps at a supply voltage of 0.5 V and a frequency of 20 GHz, is shown. The obtained results create a theoretical basis for the synthesis of low-voltage complex functional blocks with high performance and minimal occupied area, which meets modern requirements for digital applications.

S-curve Engineering for ON-state Performance using Anti-ferroelectric/Ferroelectric Stack Negative-Capacitance FinFET

<div>In this work, we report that the AFE/FE gate-stack can be utilized to engineer the S-curve for boosting the I_ON of NC-FinFET. By using a short-channel BSIM-CMG compatible AFE/FE stack NC-FinFET model, the capacitance matching and ON-state performance for AFE/FE stack NC-FinFETs are investigated. Our study indicates that, the AFE/FE gate-stack can be used to improve the capacitance matching in strong inversion at higher gate-bias. Therefore, impressively higher ON-state current (compared to single-layer) can be achieved. In reality, source-drain series resistance will make such high IDS impractical. The more likely strategy is to use lower V_DD to achieve much lower power consumption (and reduced vertical fields). While the transient NC effect also needs to be carefully investigated, this study suggests significant long term benefits to V_DD scaling if materials with certain AFE and FE properties are developed and introduced in IC manufacturing in the future.</div>

S-curve Engineering for ON-state Performance using Anti-ferroelectric/Ferroelectric Stack Negative-Capacitance FinFET

<div>In this work, we report that the AFE/FE gate-stack can be utilized to engineer the S-curve for boosting the I_ON of NC-FinFET. By using a short-channel BSIM-CMG compatible AFE/FE stack NC-FinFET model, the capacitance matching and ON-state performance for AFE/FE stack NC-FinFETs are investigated. Our study indicates that, the AFE/FE gate-stack can be used to improve the capacitance matching in strong inversion at higher gate-bias. Therefore, impressively higher ON-state current (compared to single-layer) can be achieved. In reality, source-drain series resistance will make such high IDS impractical. The more likely strategy is to use lower V_DD to achieve much lower power consumption (and reduced vertical fields). While the transient NC effect also needs to be carefully investigated, this study suggests significant long term benefits to V_DD scaling if materials with certain AFE and FE properties are developed and introduced in IC manufacturing in the future.</div>

High-Resolution Observations of a Destructive Macroburst

Shortly after 0600 UTC (midnight MDT) on 9 June 2020, a rapidly intensifying and elongating convective system produced a macroburst and extensive damage in the town of Akron on Colorado’s eastern Plains. Instantaneous winds were measured as high as 51.12 m s−1 at 2.3 m AGL from an eddy covariance (EC) tower, and a 50.45 m s−1 wind gust from an adjacent 10-m tower became the highest official thunderstorm wind gust ever measured in Colorado. Synoptic-scale storm motion was southerly, but surface winds were northerly in a post-frontal airmass, creating strong vertical wind shear. Extremely high-resolution temporal and spatial observations allow for a unique look at pressure and temperature tendencies accompanying the macroburst and reveal intriguing wave structures in the outflow. At 10-Hz frequency, the EC tower recorded a 5-hPa pressure surge in 19 seconds immediately following the strongest winds, and a 15-hPa pressure drop in the following three minutes. Surface temperature also rose 1.5°C in less than one minute, concurrent with the maximum wind gusts, and then fell sharply by 3.5°C in the following minute. Shifting wind direction observations and an NWS damage survey are suggestive of both radial outflow and a gust front passage, and model proximity soundings reveal a well-mixed surface layer topped by a strong inversion and large low-level vertical wind shear. Despite the greatest risk of severe winds forecast to be northeast of Colorado, convection-allowing model forecasts from 6-18 h in advance did show similar structures to what occurred, warranting further simulations to investigate the unique mesoscale and misoscale features associated with the macroburst.

Analog/RF Performance of Triple Material Gate Stack-Graded Channel Double Gate-Junctionless Strained-silicon MOSFET with Fixed Charges

In this paper, analog/radio frequency (RF) electrical characteristics of triple material gate stack-graded channel double gate-Junctionless (TMGS-GCDG-JL) strained-silicon (s-Si) MOSFET with fixed charges is analyzed with the help of Sentaurus TCAD. By varying the various device parameters, the analog/RF performance of the proposed TMGS-GCDG-JL s-Si MOSFET is evaluated in terms of early voltage, transconductance generation factor (TGF), voltage gain, unity current gain frequency ( ft ), unity power gain frequency (fmax ), and gain transconductance frequency product (GTFP). The results confirm that the proposed TMGS-GCDG-JL s-Si MOSFET has superior analog/RF performance compared to the gate stack-graded channel double gate-junctionless (GS-GCDG-JL) s-Si MOSFET. However, the proposed device has less transconductance and less output conductance in comparison with the GS-GCDG-JL s-Si MOSFET in strong inversion region, and reverse trend follows in sub-threshold region.

Numerical Simulations of Carrier-selective Contact Silicon Solar Cells: Role of Surface Passivation and Carrier-Selective Layers Electronic Properties

Ag/ITO/MoOx/n-Si/LiFx/Al carrier-selective contact (CSC) solar cell structures are modelled and numerically simulated based on the experimental data using an industrial quality base silicon wafer by the Sentaurus TCAD software. The role of (1) electron-selective lithium fluoride (LiFx) layer and its thickness, (2) hole-selective molybdenum oxide (MoOx) work function variation, and (3) front contact (MoOx/n-Si) surface passivation interlayer are explored on the device performance. The electron-selective LiFx layer at the rear side is led to the strong enhancement in device photocurrent by providing the electrical barrier to the minority carriers (holes) and slight improvement in open-circuit voltage, but the thickness of the layer is sensitive to efficient extraction of the majority carriers (electrons). The hole-selective MoOx layer work function needs to engineer for inducing the strong inversion layer with better built-in potential at the MoOx/n-Si junction to achieve high open-circuit voltage from a cell. A thin SiOx interlayer at the MoOx/n-Si junction has enhanced the device open-circuit voltage significantly by minimizing the minority carrier recombination at the interface.

The Dynamics of Observed Lee Waves over the Snæfellsnes Peninsula in Iceland

On 20 October 2016, aircraft observations documented a significant train of lee waves above and downstream of the Snæfellsnes Peninsula on the west coast of Iceland. Simulations of this event with the Weather Research and Forecasting (WRF) Model provide an excellent representation of the observed structure of these mountain waves. The orographic features producing these waves are characterized by the isolated Snæfellsjökull volcano near the tip of the peninsula and a fairly uniform ridge along its spine. Sensitivity simulations with the WRF Model document that the observed wave train consists of a superposition of the waves produced individually by these two dominant orographic features. This behavior is consistent with idealized simulations of a flow over an isolated 3-D mountain and over a 2-D ridge, which reproduce the essential behavior of the observed waves and those captured in the WRF simulations. Linear analytic analysis confirms the importance of a strong inversion at the top on the boundary layer in promoting significant wave activity extending far downstream on the terrain. However, analysis of the forced and resonant modes for a two layer atmosphere with a capping inversion suggest that this wave train may not be produced by resonant modes whose energy is trapped beneath the inversion. Rather, these appear to be vertically propagating modes with very small vertical group velocity that can persist far downstream of the mountain. These vertically propagating waves potentially provide a mechanism for producing near-resonant waves further aloft due to interactions with a stable layer in the mid-troposphere.

Sensitivity, Noise and Resolution in a BEOL-Modified Foundry-Made ISFET with Miniaturized Reference Electrode for Wearable Point-of-Care Applications

Ion-sensitive field-effect transistors (ISFETs) form a high sensitivity and scalable class of sensors, compatible with advanced complementary metal-oxide semiconductor (CMOS) processes. Despite many previous demonstrations about their merits as low-power integrated sensors, very little is known about their noise characterization when being operated in a liquid gate configuration. The noise characteristics in various regimes of their operation are important to select the most suitable conditions for signal-to-noise ratio (SNR) and power consumption. This work reports systematic DC, transient, and noise characterizations and models of a back-end of line (BEOL)-modified foundry-made ISFET used as pH sensor. The aim is to determine the sensor sensitivity and resolution to pH changes and to calibrate numerical and lumped element models, capable of supporting the interpretation of the experimental findings. The experimental sensitivity is approximately 40 mV/pH with a normalized resolution of 5 mpH per µm2, in agreement with the literature state of the art. Differences in the drain current noise spectra between the ISFET and MOSFET configurations of the same device at low currents (weak inversion) suggest that the chemical noise produced by the random binding/unbinding of the H+ ions on the sensor surface is likely the dominant noise contribution in this regime. In contrast, at high currents (strong inversion), the two configurations provide similar drain noise levels suggesting that the noise originates in the underlying FET rather than in the sensing region.

Colossal switchable photocurrents in topological Janus transition metal dichalcogenides

Nonlinear optical properties, such as bulk photovoltaic effects, possess great potential in energy harvesting, photodetection, rectification, etc. To enable efficient light–current conversion, materials with strong photo-responsivity are highly desirable. In this work, we predict that monolayer Janus transition metal dichalcogenides (JTMDs) in the 1T′ phase possess colossal nonlinear photoconductivity owing to their topological band mixing, strong inversion symmetry breaking, and small electronic bandgap. 1T′ JTMDs have inverted bandgaps on the order of 10 meV and are exceptionally responsive to light in the terahertz (THz) range. By first-principles calculations, we reveal that 1T′ JTMDs possess shift current (SC) conductivity as large as 2300 nm μA V−2, equivalent to a photo-responsivity of 2800 mA/W. The circular current (CC) conductivity of 1T′ JTMDs is as large as ∼104 nm μA V−2. These remarkable photo-responsivities indicate that the 1T′ JTMDs can serve as efficient photodetectors in the THz range. We also find that external stimuli such as the in-plane strain and out-of-plane electric field can induce topological phase transitions in 1T′ JTMDs and that the SC can abruptly flip their directions. The abrupt change of the nonlinear photocurrent can be used to characterize the topological transition and has potential applications in 2D optomechanics and nonlinear optoelectronics.