PreMevE: A Machine-Learning Based Predictive Model for MeV Electrons inside Earth’s Outer Radiation Belt

<p>The presence of megaelectron-volt (MeV) electrons in the Earth’s outer radiation belt poses a hazardous radiation environment for spaceborne electronics through the total ionization dose effect and deep dielectric charge/discharge phenomenon. Thus, developing a reliable forecasting model for MeV electron events has long been a critical but challenging task for space community. Here we update our recent progresses on the PREdictive model for MEV Electrons (PreMevE). This model exploits the power of machine learning algorithms, takes advantage of the coherence caused by local wave‐electron resonance, and uses electron observations from NOAA POES satellites in low‐Earth orbits as inputs—along with the upstream solar wind speeds and densities and GEO measurements—to provide high‐fidelity 1- and 2-day predictions of 1 MeV, 2 MeV and > 2 MeV electron flux distributions across the whole outer radiation belt. Using near-equatorial long-term electron data from the NASA Van Allen Probes mission, we trained, validated and demonstrated that the PreMevE model has L-shell averaged performance efficiencies of ~0.6 for out-of-sample 1-day forecasts and ~0.5 for 2-day forecasts. This study adds new science significance to an existing LEO and GEO space infrastructure, provides reliable and powerful tools to the whole space community, and also suggests for the development of more future tailored space weather models driven by similar methodologies.</p>

Greatly Enhanced Dielectric Charge Storage Capabilities of Layered Polymer Composites Incorporated with low loading fractions of Ultrathin Amorphous Iron Phosphate Nanosheets

Two-dimensional nanomaterials are promising fillers for dielectric nanocomposites because of their high specific surfaces which can induce strong interfacial polarization and result in improved dielectric permittivity. In this work, ultrathin...

Influence of nitrogen ion implantation on the electrophysical properties of the gate dielectric of power MOSFETs

Power MOS-transistors with vertical structure are investigated. Additionally, in some devices, ion implantation of nitrogen with energies of 20 and 40 keV was carried out in a dose range of 1 ⋅1013–5 ⋅ 1014 cm –2 through a sacrificial oxide 20 nm thick. For one group of wafers, rapid thermal annealing was first carried out, then oxide removal (forward order), for the other group – in the opposite sequence (reverse order). It was found that with the additional doping of nitrogen ions in doses of 1⋅1013–5 ⋅ 1013 cm –2 with energy of 20 keV, an increasing of gate dielectric charge to breakdown for both types of annealing is observed. The maximum effect occurred for the samples at a dose of nitrogen ions of 1⋅1013 cm –2 with the forward heat treatment order. This is due to the interaction of nitrogen atoms with dangling bonds of the Si – SiO2 interface during annealing, as a result of which strong chemical bonds are formed that prevent charge accumulation on the surface of the Si – SiO2 interface. It is assumed that the main contribution to the gate leakage current is made by the tunneling of charge carriers through traps.

Instability and Drift Phenomena in Switching RF-MEMS Microsystems

MEMS switches include mobile beams in their mechanical structure and these suspended parts are essential for the device functioning. This paper illustrates the most important instability phenomena related to MEMS switches. Starting from the most important instability exploited in these devices—the electrical actuation—the paper also analyzes other important effects related to instability phenomena, which are very common in this type of technology. Instabilities due to dielectric charge trapping, fabrication tolerances, mechanical deformation, contact wear, and temperature variation are duly analyzed, giving a comprehensive view of the complexity encountered in the reliable functioning of these apparently simple devices.

A Case Study of Trapped Charge Induced Surface Leakage

In many cases, the leakage is relatively small and tends to spread out over a relatively large area. While diagnostic techniques using laser stimulation, such as OBIRCH, or photoemission are powerful in identifying localized defects in silicon crystal and backend metal layers, they are found to be not as sensitive in isolating charge induced leakage. This paper presents a case study of dielectric charge induced leakage in a high voltage ESD device. In this case, conventional photoemission and laser probing diagnostic techniques were not able to localize leakage sites. By using atomic force probing for detailed electrical characterization of individual devices, experimenting with UV radiation, and SCM 2D dopant profiling analysis, it showed that trapped charges in dielectric layers cause leakage near silicon surface. Based on the finding, the FAB fixed the issue by implementing UV bake in the process.

Non-Visual Defect Monitoring with Surface Voltage Mapping: Application for Semiconductor IC and PV Technology

Non Visual Defects (NVD) is a category of defects that cause electrical failures but are not detected with visual wafer inspection tools. Our approach for NVD detection is based on the Kelvin probe surface voltage mapping technique. The detection of defects is enhanced using field-effect created in a non-contact manner by corona charge deposition on the surface of semiconductor. Precise defect location is accomplished with surface voltage gradient magnitude mapping that enhances delineation of defects. Detected defects are characterized locally using the corona-voltage technique or isothermal voltage transient decay analysis. Presented examples include: dielectric charge and interfacial defect mapping on 300mm Si wafers; deep level emission mapping on epitaxial SiC and mobile ion mapping in Si solar cells.