Topographic elevation change through tracking shadow cast from mountain ridges. Showcasing Red Glacier, Mt. Iliamna.

<p>Continuous global monitoring of glacier elevation change over decadal timescales is difficult to establish. Dedicated stereoscopic satellite missions are scarce and had, up to recently, limited spatial coverage. By contrast, observations from monoscopic satellites providing continuous global coverage extending for several decades backwards in time, is readily available. Therefore, we explore the potential of this type of imagery for extracting elevation change. This is done through tracking of moving shadows, which is a new and simple technique we call photohypsometry. The known sun angles and clear shadow patterns on the glacier surface, establish a simple trigonometric relationship, enabling the extraction of elevation change. </p><p>Here we showcase the methodology on Red Glacier, a glacier situated on the Eastern flank of Iliamna volcano, Alaska. A tributary of this glacier has fast surface speed in its snout, slightly shifting lateral moraines, but no known surge history. Shadow from neighboring mountain ridges cast on the accumulation region of this glacier, so a clear time-series can be constructed from Sentinel-2 imagery.</p><p>This example highlights the potential of this technique. While the coverage of topographic information does not cover the whole glacial basin, it can complement other data sources. It is especially suited for small mountain glaciers and thrives in brightly reflecting snow-covered accumulation areas.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.b09d70b5a60068638401161/sdaolpUECMynit/12UGE&app=m&a=0&c=32160e0988a69f5c02b961f9deba60a8&ct=x&pn=gepj.elif&d=1" alt=""></p>

Theoretical limits and new approaches to reconstruct temperature from the isotopic composition of ice cores in low-accumulation regions

<p>For several decades, ice-core water-isotope research was focused on retrieving and interpreting single cores, measured on increasingly finer resolution and higher analytic precision. However, not only the sampling resolution or analytical precision limits the ability to recover the climate signal, but also the way the climatic signal is imprinted in the isotopic composition profile obtained from ice cores. Therefore, despite three decades of Antarctic ice-coring and dozens of firn cores, especially the temperature evolution in the low accumulation region of East Antarctica during the last millennium is still barely known.  In the recent years, strong progress has been made in the understanding of the isotopic signal formation based on process studies, snow pits, snow trenches and replicate cores. Using this knowledge, we will review the limits of temperature reconstructions based on theoretical considerations, empirical signal-to-noise ratio estimates and forward models of the signal formation. We will further discuss new avenues for sharpening the ability to recover high-resolution temperature signals from firn and ice cores by optimally combining multiple cores and by combining isotope with impurity records.</p>

High altitude accumulation and preserved climate information in the western Pamir, observations from the Fedchenko Glacier accumulation basin

The accumulation region of Fedchenko Glacier represents an extensive snow reservoir in the Pamir Mountains feeding the longest glacier in Central Asia. Observed elevation changes indicate a continuous ice loss in the ablation region of Fedchenko Glacier since 1928, while the mass balance of the accumulation region is largely unknown. In this study, we show that accumulation varies considerably in the main accumulation basin, with accumulation rates up to 2400 mm w.e. a−1 in the West, decreasing to <1000 mm w.e. a−1 in the center, although the elevation difference is <200 m. The combination of snow/firn samples and ground-penetrating radar profiles suggests that this accumulation pattern is persistent during the recent past. The recent accumulation history is reconstructed from internal radar reflectors using a firn densification model and shows strong interannual variations, but near constant mean values since 2002. Modeling of trajectories, based on accumulation and glacier geometry, results in an estimate of the depth/age relation close to the main divide. This region provides one of the most suitable locations for retrieving climate information with temporal high resolution for the last millennium, with a potential to cover most of the Holocene in less detail.

Study of HCI Reliability for PLDMOS

In this paper, we demonstrate electrical degradation due to hot carrier injection (HCI) stress for PLDMOS device. The lower gate current and the IDsat degradation at low gate voltage (VGS) and high drain voltage (VDS) is investigated. Hot Electrons, generated by impact ionization during stress, are injected into the gate oxide, creating negative fixed oxide charges and interface-states above the accumulation region and the channel. Increase of the drain-source current is induced by the negative fixed oxide charges. The physical model of the degradation has been proven combining experimental data and TCAD simulations.

Functional Oxide as an Extreme High-k Dielectric towards 4H-SiC MOSFET Incorporation

MOS Capacitors are demonstrated on 4H-SiC using an octahedral ABO3 ferroic thin-film as a dielectric prepared on several buffer layers. Five samples were prepared: ABO3 on SiC, ABO3 on SiC with a SiO2 buffer (10 nm and 40 nm) and ABO3 on SiC with an Al2O3 buffer (10nm and 40 nm). Depending on the buffer material the oxide forms in either the pyrochlore or perovskite phase. A better lattice match with the Al2O3 buffer yields a perovskite phase with internal switchable dipoles. Hysteresis polarization-voltage loops show an oxide capacitance of ~ 0.2 μF/cm2 in the accumulation region indicating a dielectric constant of ~120.

Study of the side gate junctionless transistor in accumulation region

Purpose The purpose of this paper is to analyse the operation of p-type side gate junctionless silicon transistor (SGJLT) in accumulation region through experimental measurements and 3-D TCAD simulation results. The variation of electric field components, carrier’s concentration and valence band edge energy towards the accumulation region is explored with the aim of finding the origin of SGJLT performance in the accumulation operational condition. Design/methodology/approach The device is fabricated by atomic force microscopy nanolithography on silicon-on-insulator wafer. The output and transfer characteristics of the device are obtained using 3-D Technology Computer Aided Design (TCAD) Sentaurus software and compared with experimental measurement results. The advantages of AFM nanolithography in contact mode and Silicon on Insulator (SOI) technology were implemented to fabricate a simple structure which exhibits the behaviour of field effect transistors. The device has 200-nm channel length, 100-nm gate gap and 4 μm for the distance between the source and drain contacts. The characteristics of the fabricated device were measured using an Agilent HP4156C semiconductor parameter analyzer (SPA). A 3-D TCAD Sentaurus tool is used as the simulation platform. The Boltzmann statistics is adopted because of the low doping concentration of the channel. Hydrodynamic model is taken to be as the main transport model for all simulations, and the quantum mechanical effects are ignored. A doping dependent Masetti mobility model was also included as well as an electric field dependent model with Shockley–Read–Hall (SRH) carrier recombination/generation. Findings We have obtained that the device is a normally on state device mainly because of the lack of work functional difference between the gate and the channel. Analysis of electric field components’ variation, carrier’s concentration and valence band edge energy reveals that increasing the negative gate voltage drives the device into accumulation region; however, it is unable to increase the drain current significantly. The positive slope of the hole quasi-Fermi level in the accumulation region presents mechanism of carriers’ movement from source to drain. The influence of electric field because of drain and gate voltage on charge distribution explains a low increasing of the drain current when the device operates in accumulation regime. Originality/value The proposed side gate junctionless transistors simplify the fabrication process, because of the lack of gate oxide and physical junctions, and implement the atomic force microscopy nanolithography for fabrication process. The optimized structure with lower gap between gate and channel and narrower channel would present the output characteristics near the ideal transistors for next generation of scaled-down devices in both accumulation and depletion region. The presented findings are verified through experimental measurements and simulation results.