Kr and N implantations in a stainless steel AISI304L: thermal evolution

The evolution of nitrides produced by N-implantation of stainless steel samples previously bombarded with Kr and annealed up to temperature corresponding to 0.5 of the melting point is studied. Transmission electron microscopy shows the size evolution of the bubbles. The dependence of the bubbles on the nitride evolution is established by conversion electron Mössbauer spectroscopy and a retention of -(Fe,Cr,Ni)_{2 + x}N up to 400°C was observed. Between 450 °C and 650 °C the presence of a magnetic field characteristic of the -Fe phase was observed. The evolution of the N-profile was obtained by nuclear reaction analysis.     

Wetting conditions and microstructural characteristics of a fired B4C-containing MgO carbon brick

This investigation is a continuation of the studies of the use of boron carbide as an antioxidant in refractory carbon-containing materials. The previous studies were concerned with the stability of boron carbide at high temperatures. The present work gives an account of the wetting conditions and microstructural characteristics of a fired MgO-C brick containing boron carbide additive. The results obtained show that a contribution may be made to the oxidation-inhibiting protective action of the carbide by the formation of a continuous network of dense bridges of borate melts between periclase grains. A white layer with a high percentage of magnesium borate is produced between the decarbonized and non-decarbonized material. The nature of this layer is similar to that from secondary MgO in MgO-C bricks with no additive. The occurrence of this layer is the subject of further research.     

2-D characterization of dynamic charge distribution in MOScontrolled thyristors: experiment and simulation

The MOS-controlled thyristor (MCT) is well suited for very high power applications. The maximum capability of turn-off currents for p-channel MCT's was so far limited to low values (<10 A at 1000 V snubberless switching) due to strong sublinear current scaling with respect to the device area. In this letter we investigate this phenomenon by full device scale transient carrier distribution measurements and simulations. For the first time the degradation of the switching performance for highly structured and shorted base MOS thyristors is related by measurement to an inhomogeneous current distribution in the device during switching. These measurements confirm predictions of the effect by device simulation     

Overcoming the Interfacial Limitations Imposed by the Solid–Solid Interface in Solid‐State Batteries Using Ionic Liquid‐Based Interlayers

Li‐garnets are promising inorganic ceramic solid electrolytes for lithium metal batteries, showing good electrochemical stability with Li anode. However, their brittle and stiff nature restricts their intimate contact with both the electrodes, hence presenting high interfacial resistance to the ionic mobility. To address this issue, a strategy employing ionic liquid electrolyte (ILE) thin interlayers at the electrodes/electrolyte interfaces is adopted, which helps overcome the barrier for ion transport. The chemically stable ILE improves the electrodes‐solid electrolyte contact, significantly reducing the interfacial resistance at both the positive and negative electrodes interfaces. This results in the more homogeneous deposition of metallic lithium at the negative electrode, suppressing the dendrite growth across the solid electrolyte even at high current densities of 0.3 mA cm^?2. Further, the improved interface Li/electrolyte interface results in decreasing the overpotential of symmetric Li/Li cells from 1.35 to 0.35 V. The ILE modified Li/LLZO/LFP cells stacked either in monopolar or bipolar configurations show excellent electrochemical performance. In particular, the bipolar cell operates at a high voltage (≈8 V) and delivers specific capacity as high as 145 mAh g^?1 with a coulombic efficiency greater than 99%.     

In situ TEM studies of micron‐sized all‐solid‐state fluoride ion batteries: Preparation,prospects, and challenges

Trustworthy preparation and contacting of micron‐sized batteries is an essential task to enable reliable in situ TEM studies during electrochemical biasing. Some of the challenges and solutions for the preparation of all‐solid‐state batteries for in situ TEM electrochemical studies are discussed using an optimized focused ion beam (FIB) approach. In particular redeposition, resistivity, porosity of the electrodes/electrolyte and leakage current are addressed. Overcoming these challenges, an all‐solid‐state fluoride ion battery has been prepared as a model system for in situ TEM electrochemical biasing studies and first results on a Bi/La_0.9Ba_0.1F_2.9 half‐cell are presented. Microsc. Res. Tech. 79:615–624, 2016. © 2016 Wiley Periodicals, Inc.     

A comprehensive VCSEL device simulator

This paper deals with the design and implementation of a self-consistent electrothermooptical device simulator for vertical-cavity surface-emitting lasers (VCSELs). The model is based on the photon rate equation approach. For the bulk electrothermal transport, a thermodynamic model is employed in a rotationally symmetric body. Heterojunctions are modeled using a thermionic emission model and quantum wells are treated as scattering centers for carriers. The optical field is expanded into modes that are eigensolutions of the vectorial electromagnetic wave equation with an arbitrary, complex dielectric function. The open nature of the VCSEL cavity is treated by employing perfectly matched layers. The optical gain and absorption model in the quantum-well active region is based on Fermi's Golden Rule. The subbands in the quantum well are determined by solving the stationary Schrodinger equation and using a parabolic band approximation for the electrons, light and heavy holes. The photon rate equation is fully integrated into the Newton-Raphson scheme used to solve the system of nonlinear device equations. An efficient numerical optical mode solver is used, that is based on a Jacobi-Davidson type iterative eigensolver. The latter combines a continuation scheme with preconditioner recycling. The practical relevance of the implementation is demonstrated with the simulation of a realistic etched-mesa VCSEL device.     

Monte Carlo, Hydrodynamic and Drift-Diffusion Simulation of Scaled Double-Gate MOSFETs

Double-gate MOSFETs with gate lengths of 50 and 25 nm are theoretically analyzed by drift-diffusion (DD), hydrodynamic (HD) and self-consistent full-band Monte Carlo (MC) simulation. The underestimation of the on-current I _on by DD is found to be stronger than the overestimation by HD. The main differences to the case of bulk MOSFETs are: (i) not only the velocities in the source-side of the channel, but also the sheet densities vary appreciably between the different transport models, (ii) current conservation leads to strong non-equilibrium in the highly doped source region with high velocities and electric fields and (iii) surface roughness appears to become more effective for reduced silicon film thicknesses which might jeopardize the performance enhancement upon further scaling.     

Single-electron device simulation

A three-dimensional (3-D) simulator is presented which uses a linear-response approach to simulate the conductance of semiconductor single-electron transistors at the solid-state level. The many-particle groundstate of the quantum dot, weakly connected to the drain and the source reservoir, is evaluated in a self-consistent manner including quantum-mechanical many-body interactions. A transfer-Hamiltonian approach is used to compute the tunneling rates for the coupling of the quantum dot levels to the macroscopic reservoirs on the basis of realistic barrier potentials. The simulator was applied to a GaAs/AlGaAs example structure. We discuss the conductance characteristic and the capacitances as well as the microscopic structure of the quantum dot