The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE FWHM/E≈15 %. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance.

https://link.springer.com/content/pdf/10.1007%2Fs11214-013-9968-7.pdf

Helium, Oxygen, Proton, and Electron (HOPE) Mass Spectrometer for the Radiation Belt Storm Probes Mission

Organic–inorganic hybrid perovskite solar cells with mixed cations and mixed halides have achieved impressive power conversion efficiency of up to 22.1%. Phase segregation due to the mixed compositions has attracted wide concerns, and their nature and origin are still unclear. Some very useful analytical techniques are controversial in microstructural and chemical analyses due to electron beam-induced damage to the “soft” hybrid perovskite materials. In this study photoluminescence, cathodoluminescence, and transmission electron microscopy are used to study charge carrier recombination and retrieve crystallographic and compositional information for all-inorganic CsPbIBr2 films on the nanoscale. It is found that under light and electron beam illumination, “iodide-rich” CsPbI(1+x)Br(2−x) phases form at grain boundaries as well as segregate as clusters inside the film. Phase segregation generates a high density of mobile ions moving along grain boundaries as ion migration “highways.” Finally, these mobile ions can pile up at the perovskite/TiO2 interface resulting in formation of larger injection barriers, hampering electron extraction and leading to strong current density–voltage hysteresis in the polycrystalline perovskite solar cells. This explains why the planar CsPbIBr2 solar cells exhibit significant hysteresis in efficiency measurements, showing an efficiency of up to 8.02% in the reverse scan and a reduced efficiency of 4.02% in the forward scan, and giving a stabilized efficiency of 6.07%.

Phase segregation enhanced ion movement in efficient inorganic CsPbIBr2 solar cells

The role of the alkali metal cations in halide perovskite solar cells is not well understood. Using synchrotron-based nano-x-ray fluorescence and complementary measurements, we found that the halide distribution becomes homogenized upon addition of cesium iodide, either alone or with rubidium iodide, for substoichiometric, stoichiometric, and overstoichiometric preparations, where the lead halide is varied with respect to organic halide precursors. Halide homogenization coincides with long-lived charge carrier decays, spatially homogeneous carrier dynamics (as visualized by ultrafast microscopy), and improved photovoltaic device performance. We found that rubidium and potassium phase-segregate in highly concentrated clusters. Alkali metals are beneficial at low concentrations, where they homogenize the halide distribution, but at higher concentrations, they form recombination-active second-phase clusters.

/pdf/homogenized-halides-and-alkali-cation-segregation-in-alloyed-4xxftf47zn.pdf

Homogenized halides and alkali cation segregation in alloyed organic-inorganic perovskites

Helium Ion Microcopy (HIM) based on Gas Field Ion Sources (GFIS) represents a new ultra high resolution microscopy and nano-fabrication technique. It is an enabling technology that not only provides imagery of conducting as well as uncoated insulating nano-structures but also allows to create these features. The latter can be achieved using resists or material removal due to sputtering. The close to free-form sculpting of structures over several length scales has been made possible by the extension of the method to other gases such as Neon. A brief introduction of the underlying physics as well as a broad review of the applicability of the method is presented in this review.

/pdf/helium-ion-microscopy-20lveyia0z.pdf

Helium ion microscopy

Space-Weathering of Solar System Bodies: A Laboratory Perspective

Monte Carlo softwares are widely used to understand the capabilities of electron microscopes. To study more realistic applications with complex samples, 3D Monte Carlo softwares are needed. In this article, the development of the 3D version of CASINO is presented. The software feature a graphical user interface, an efficient (in relation to simulation time and memory use) 3D simulation model, accurate physic models for electron microscopy applications, and it is available freely to the scientific community at this website: www.gel.usherbrooke.ca/casino/index.html. It can be used to model backscattered, secondary, and transmitted electron signals as well as absorbed energy. The software features like scan points and shot noise allow the simulation and study of realistic experimental conditions. This software has an improved energy range for scanning electron microscopy and scanning transmission electron microscopy applications.

Three-Dimensional Electron Microscopy Simulation with the CASINO Monte Carlo Software

SiO2 shallow nanostructures ICP etching using ZEP electroresist

This paper presents a damascene process for the fabrication of titanium micro/nanostructures and nanowires with adjustable thickness down to 2?nm. Their depth is precisely controlled by chemical?mechanical planarization together with in-process electrical characterization. The latter, in combination with a model of the titanium resistivity versus thickness, allows control of the metal line depth in the nanometer range. In summary, we have developed a planarization end point detection method for metal nanostructures. In addition, the model adopted covers geometrical influences like oxidation and ageing. The fabricated titanium nanowire test structures have a thickness ranging from 2 to 25?nm and a width ranging between 15 and 230?nm.

http://iopscience.iop.org/article/10.1088/0957-4484/24/24/245305/pdf

A damascene platform for controlled ultra-thin nanowire fabrication.

The development of metallic single-electron transistor (SET) depends on the downscaling and the electrical properties of its tunnel junctions (TJs) These TJs should insure high-ON current, low-OFF current, and low capacitance We propose an engineered TJ based on multidielectric stacking A number of high- $k$ and low- $k$ materials were considered to optimize the TJ’s characteristics The optimized TJ is proven to increase the $I_{\mathrm{{\scriptscriptstyle ON}}}$ current and the $I_{\mathrm{{\scriptscriptstyle ON}}}/I_{\mathrm{{\scriptscriptstyle OFF}}}$ ratio in a double-gate SET Using TiO2 plasma oxidation and Al2O3 atomic layer deposition, an SET proof of concept, with a double layer TJ, was fabricated and characterized

Tunnel Junction Engineering for Optimized Metallic Single-Electron Transistor

A novel analytical and compact model of Single Electron Transistor (SET) is developed and implemented in Verilog-A language for use in hybrid SET-CMOS logic circuit design. The model is based on the steady state Master-Equation (ME). The implementation of this original and simple model, taking into account physical characteristics of tunnel junctions and the thermionic emission, has faithfully reproduced the behavior of metallic SET operating at room temperature. The hybrid SET-CMOS universal logic gate cell is analyzed to illustrate the efficiency of this compact SET model.

Marc Guilmain

Papers

Three-Dimensional Electron Microscopy Simulation with the CASINO Monte Carlo Software

SiO2 shallow nanostructures ICP etching using ZEP electroresist

A damascene platform for controlled ultra-thin nanowire fabrication.

Tunnel Junction Engineering for Optimized Metallic Single-Electron Transistor

Single Electron Transistor analytical model for hybrid circuit design