Papers by Keyword: Diffusion Barrier

Abstract: In order to make SiC devices more accessible for high-temperature applications, reliable ohmic contacts and metallization systems which can also withstand extended operation at high temperatures are needed. In this work, metal layer stacks containing Ag, Ti, TiN, Ni and NiAl, where NiAl refers to a mixture of 97,4 wt% Ni and 2,6 wt% Al, were deposited on Si and SiC samples and consecutively thermally aged at 400 °C for 100 h in air. Mesa structures were found to be challenging for keeping oxygen from diffusing through the metal stack to the substrate. On flat surfaces, diffusion barriers were successfully used to protect the ohmic contact on 4H-SiC samples from oxidizing. Diffusion barriers made of TiN were found to show pore formation after the thermal treatment. The reason for the pores is thought to be gas formation, which is believed to be the result of the TiN layers containing too much nitrogen. The exact chemical composition of TiN layers therefore seems to be of vital importance for high-temperature applications.

Abstract: Recently, two-dimensional (2D) materials have been rapidly developed and they provided a wide application on the anode of the batteries, reducing the adverse effect of traditional ion batteries including low capacity, short cycle life, low charging rate and poor safety mainly coming from the use of graphite anode. The current report investigates the anode performances of AlSi, a new 2D material exfoliated from NaAlSi, for Li ion batterys (LIBs) through density functional theory (DFT) calculations and gives quantitative discussions on the Li ion valences, binding energies and open-circuit voltages of 2D AlSi anode. The results indicate that 2D AlSi performs great as a novel anode due to the moderate adhesion to Li and low barrier for ion diffusion. Furthermore, our research results illustrate a broad application prospect on the new anode inventions as well as reducing useless consumption on the batteries by the practice of AlSi anode.

Abstract: Recently, two-dimensional (2D) material developed rapidly and provided a wide application on the anode of the batteries, reducing the adverse effect of traditional ion batteries such as low capacity, short cycle life, slow charging and poor safety mainly coming from the use of graphite anode. The current report investigates the anode performances of phosphorus, a new 2D material in electrochemistry field, with monolayer and bilayer structure for Li ion batterys (LIBs) through density functional theory (DFT) calculations and gives a comparison on the Li ion valences, binding energies and open-circuit voltages between the two structures. The results indicate that bilayer phosphorus perform better as a novel anode due to the stronger adhesion to Li and lower barrier for ion diffusion. Furthermore, our research results illustrate a broad application prospect on the new anode inventions as well as reducing useless consumption on the batteries by the practice of bilayer phosphorus anode.

Abstract: Due to the development of various mobile electronic devices, such as electric vehicles, rechargeable ion batteries are becoming more and more important. However, the current commercial lithium-ion batteries have obvious defects, including poor safety from Li dendrite and flammable electrolyte, quick capacity loss and low charging and discharging rate. It is very important to find a better two-dimensional material as the anode of the battery to recover the disadvantages. In this paper, first principles calculations are used to explore the performances of VS₂ bilayer and VS₂ / graphene heterostructure as the anodes of Li ion batteries. Based on the calculation of the valences, binding energy, intercalation voltage, charge transfer and diffusion barrier of Li, it is found that the latter can be used as a better anode material from the perspective of insertion voltage and binding energy. At the same time, the former one is better in terms of diffusion barrier. Our study provides a comprehensive understanding on VS₂ based 2D anodes.

Abstract: The paper presents the results of research on the creation of heat-resistant composite A5-Cr-St3 with diffusion barrier. It considers the influence of the thickness of the chromium layer and the kinematic parameters of the structure and thermal steel-aluminum composite.

Abstract: Silicide formation by reactive diffusion is of interest in numerous applications especially for contact formation and interconnections in microelectronics. Several reviews have been published on this topic and the aim of this chapter is to provide an update of these reviews by focusing on new experiment results. This chapter presents thus some progress in the understanding of the main mechanisms (diffusion/reaction, nucleation, lateral growth…) for thin and very thin films (i.e. comprised between 4 and 50 nm). Recent experimental results on the mechanisms of formation of silicide are presented and compared to models and/or simulation in order to extract physical parameters that are relevant to reactive diffusion. These mechanisms include nucleation, lateral growth, diffusion/interface controlled growth, and the role of a diffusion barrier. The combination of several techniques including in situ techniques (XRD, XRR, XPS, DSC) and high resolution techniques (APT and TEM) is shown to be essential in order to gain understanding in the solid state reaction in thin films and to better control these reaction for making contacts in microelectronics devices or for other application.

Abstract: We report the initial results of using co-sputtered Pt:Ti 80:20 at. % composition ratio metallization as a diffusion barrier against gold (Au) and oxygen (O), as an interconnect layer, as well as forming simultaneous ohmic contacts to n-and p-type 4H-SiC. Having a single conductor with such combined multi-functional attributes would appreciably reduce the fabrication costs, processing time and complexity that are inherent in the production of SiC based devices. Auger Electron Spectroscopy, Focused Ion Beam-assisted Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy analyses revealed no Au and O migration to the SiC contact surface and minimal diffusion through the Pt:Ti barrier layer after 15 minutes of exposure at 800 oC in atmosphere, thus offering potential long term stability of the ohmic contacts. Specific contact resistance values of 7 x 10^-5 and 7.4 x 10^-4 Ω-cm² were obtained on the n (N_d=7 x 10¹⁸ cm^-3) and p (N_a=2 x 10²⁰ cm^-3) -type 4H-SiC, respectively. The resistivity of 75 μΩ-cm was obtained for the Pt:Ti layer that was sandwiched between two SiO₂ layers and annealed in pure O ambient up to 900 °C, which offers promise as a high temperature interconnect metallization.

Abstract: Monolithic fuel plates have been developed utilizing low enriched U alloyed with 10 wt.% Mo to replace highly enriched fuels in research and test reactors, in accordance with the goals of the Materials Management and Minimization Reactor Conversion Program. The fuel plates consist of U10Mo fuel, Zr diffusion barrier, and AA6061 cladding. They are fabricated by co-rolling the U10Mo and Zr, which are then encapsulated via hot isostatic pressing of the entire U10Mo/Zr/AA6061 assembly. During fabrication, the metal constituents of the fuel plates undergo phase transformations as well as interdiffusion and reactions at interfaces. The areas of interest are the U10Mo fuel, U10Mo/Zr interface, U10Mo/AA6061 interface, Zr/AA6061 interface, and AA6061-AA6061 bond line. Knowledge of the transformations and growth in the plates is necessary to optimize fabrication parameters and predict behavior as they relate to irradiation performance. Numerous studies have been conducted to analyze these reactions in monolithic fuel plates, and a summary of their observations is provided in this paper.

Abstract: Monolithic fuel system with U – 10 wt.% Mo (U10Mo) fuel alloy has been developed for the Materials Management and Minimization reactor conversion program to replace highly-enriched fuels in research and test reactors with low-enriched fuels. Interdiffusion and phase transformations in the system constituents, i.e., U10Mo fuel, AA6061 cladding, and Zr diffusion barrier, have been investigated using fuel plates fabricated via rolling and hot-isostatic pressing. Diffusion couples, utilizing the constituents of the fuel system were also carried out to help understand the findings from fuel plates based on phase equilibria and diffusion kinetics. Findings from both fuel plates and diffusion couples can provide a comprehensive knowledge to assess, model, and predict the performance of monolithic low-enriched fuel system from fabrication to irradiation. This paper summarizes the experimental results reported from characterization of the fuel plates and diffusion couples with emphasis on interactions at the fuel-cladding, fuel-diffusion barrier, cladding-diffusion barrier, and cladding-cladding interfaces. Constituent phases and relevant diffusion kinetics are compared and contrasted, taking into account differences in thermodynamics and kinetics variables such as pressure, temperature, and cooling rate.

Abstract: In this work we report the results of a set of experiments carried out to assess the ability of recombination lifetime measurements for the detection of palladium contamination in silicon. Palladium is found to be a very effective recombination center, so recombination lifetime measurements are a very sensitive method to detect palladium in silicon. The surface segregation of palladium was monitored by the reduction of its recombination activity in the silicon volume. The palladium segregation at the wafer surface was checked by selective etching, and by Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) analysis.After validating recombination lifetime measurements for palladium detection, we use these measurements to define suitable approaches to the prevention of palladium contamination of silicon devices. The efficiency of a diffusion barrier layer (silicon nitride) and of decontamination by wet cleaning are tested.