Production and annealing of defects in Li-diffused silicon after 30-MeV electron irradiation at 300 K
Production and annealing of defects in lithium diffused silicon after electron irradiation
Berger, R. A.↗
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Results for “SILICON 30”
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Progress Towards Extended Cycle Life Si-based Anodes: Investigation of Fluorinated Local High Concentration Electrolytes
Silicon (Si) anodes are promising candidates for Li-ion batteries due to their high specific capacity and low operating potential. Implementation has been challenged by the significant Si volume changes during (de)lithiation and associated growth/regrowth of the solid electrolyte interphase (SEI). In this report, fluorinated local high concentration electrolytes (FLHCEs) were designed such that each component of the electrolyte (solvent, salt, diluent) is fluorinated to modify the chemistry and stabilize the SEI of high (30%) silicon content anodes. FLHCEs were formulated to probe the electrolyte salt concentration and ratio of the fluorinated carbonate solvents to a hydrofluoroether diluent. Higher salt concentrations led to higher viscosities, conductivities, and contact angles on polyethylene separators. Electrochemical cycling of Si-graphite/NMC622 pouch cells using the FLHCEs delivered up to 67% capacity retention after 100 cycles at a C/3 rate. Post-cycling X-ray photoelectron spectroscopy (XPS) analyses of the Si-graphite anodes indicated the FLHCEs formed a LiF rich solid electrolyte interphase (SEI). The findings show that the fluorinated local high concentration electrolytes contribute to stabilizing the Si-graphite electrode over extended cycling.
36 MATERIALS SCIENCE↗
The {sup 30}P(p, γ){sup 31}S reaction in classical novae: progress and prospects
The unknown thermonuclear rate of the {sup 30}P(p, γ){sup 31}S reaction at classical-nova temperatures currently prohibits the accurate modeling of nova nucleosynthesis in the A ⩾ 30 region. This is hindering the calibration of nova thermometers based on observed O/S, S/Al, O/P, and P/Al abundance ratios in nova ejecta, the calibration of a meter to probe mixing at the core-envelope interface in novae based on the observed Si/H abundance ratio, and the identification of candidate pre-solar nova grains found in primitive meteorites based on laboratory measurements of their {sup 30}Si/{sup 28}Si isotopic ratios. Each of these diagnostics could address key questions in our understanding of classical novae if the {sup 30}P(p, γ){sup 31}S rate were known. We review progress on the determination of the {sup 30}P(p, γ){sup 31}S rate leading to a critical assessment of current interpretations of published data and prospects for future work.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Oxygen and silicon isotope ratios of lunar rock 12013
Apollo 12 lunar rock 12013 oxygen 18 and silicon 30 ratios, comparing to terrestrial basalts and gabbros, Apollo 11 rocks and oceanic rhyolite obsidians
Epstein, S.↗
Developmental program for 8-watt, 2.3- gigahertz, n-p-n, silicon transistor Final report, 12 Oct. 1966 - 30 Oct. 1968
Silicon microwave transistor with hermetic coaxial package
Hodowanec, G.↗
Development of 30 micrometers extrinsic silicon multiplexed infrared deterctor array
Two hybrid infrared (IR) detector arrays of antimony-doped silicon (Si:Sb) were produced and tested to evaluate their potential for use in low-background IR astronomy applications. The format of the arrays is 58 x 62 elements, with 76 micron-square pixels. A random-access, switched metal-oxide semiconductor field effect transistor (MOSFET) silicon multiplexer is used to read out the array elements. Reduced-background tests of signal, noise, and noise equivalent power were conducted over the temperature range 3.2 to 12 K. The arrays were found to have good sensitivity and good uniformity.
Orias, G.↗
Production and annealing of defects in lithium-diffused silicon after irradiation with 30-MeV electrons and fission neutrons at 300 K
Production and annealing of defects in lithium diffused bulk silicon after irradiation with 30 MeV electrons and fission neutrons at 300 K
Berger, R. A.↗
Near- to mid-IR refractive index of {sup 28}Si, {sup 29}Si and {sup 30}Si monoisotopic single crystals
We have prepared {sup 28}Si, {sup 29}Si and {sup 30}Si single crystals with enrichments above 99.9 at % and a silicon single crystal of natural isotopic composition. The oxygen and carbon concentrations in all the crystals are within 5x10{sup 15} cm{sup -3}, and the content of metal impurities is 0.01 - 0.1 ppma. The refractive index of the crystals has been determined in the range 1.05-25.5 {mu}m using interference refractometry, and its dispersion and material dispersion have been determined. (letters)
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Nuclear Data Sheets for A = 30
Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for {sup 30}F, {sup 30}Ne, {sup 30}Na, {sup 30}Mg, {sup 30}Al, {sup 30}Si, {sup 30}P, {sup 30}S, and {sup 30}Cl. This evaluation for A=30 supersedes the previous evaluation 1998En04. However, some additional information for these nuclides can be found in earlier evaluations 1990En08 and 1978En02. Highlights of this publication are the following: The latest studies (2010StZZ, 2010De26) by fusion evaporation reaction of {sup 14}C and {sup 18}O using GAMMASPHERE array, consisted of 101 Compton-suppressed HPGe detectors, provided new data for {sup 30}Al, {sup 30}Si, and {sup 30}Mg nuclides and extended the level scheme to higher spin states. 2010Se07 reported a new level at 4814(3) keV for {sup 30}S nuclide studied by the {sup 32}S(p,t) reaction. It did not observe the 5168(6) keV level that was reported earlier as a possible doublet by 2007Ba69. In the absence of further experiment, 2010Se07 considers the level as one of the doublets.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Low-energy dipole excitations in neon isotopes and N=16 isotones within the quasiparticle random-phase approximation and the Gogny force
Low-energy dipole excitations in neon isotopes and N=16 isotones are calculated with a fully consistent axially-symmetric-deformed quasiparticle random phase approximation (QRPA) approach based on Hartree-Fock-Bogolyubov (HFB) states. The same Gogny D1S effective force has been used both in HFB and QRPA calculations. The microscopical structure of these low-lying resonances, as well as the behavior of proton and neutron transition densities, are investigated in order to determine the isoscalar or isovector nature of the excitations. It is found that the N=16 isotones {sup 24}O, {sup 26}Ne, {sup 28}Mg, and {sup 30}Si are characterized by a similar behavior. The occupation of the 2s{sub 1/2} neutron orbit turns out to be crucial, leading to nontrivial transition densities and to small but finite collectivity. Some low-lying dipole excitations of {sup 28}Ne and {sup 30}Ne, characterized by transitions involving the {nu}1d{sub 3/2} state, present a more collective behavior and isoscalar transition densities. A collective proton low-lying excitation is identified in the {sup 18}Ne nucleus.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
STELLAR ORIGINS OF EXTREMELY {sup 13}C- AND {sup 15}N-ENRICHED PRESOLAR SIC GRAINS: NOVAE OR SUPERNOVAE?
Extreme excesses of {sup 13}C ({sup 12}C/{sup 13}C < 10) and {sup 15}N ({sup 14}N/{sup 15}N < 20) in rare presolar SiC grains have been considered diagnostic of an origin in classical novae, though an origin in core collapse supernovae (CCSNe) has also been proposed. We report C, N, and Si isotope data for 14 submicron- to micron-sized {sup 13}C- and {sup 15}N-enriched presolar SiC grains ({sup 12}C/{sup 13}C < 16 and {sup 14}N/{sup 15}N < ∼100) from Murchison, and their correlated Mg–Al, S, and Ca–Ti isotope data when available. These grains are enriched in {sup 13}C and {sup 15}N, but with quite diverse Si isotopic signatures. Four grains with {sup 29,30}Si excesses similar to those of type C SiC grains likely came from CCSNe, which experienced explosive H burning occurred during explosions. The independent coexistence of proton- and neutron-capture isotopic signatures in these grains strongly supports heterogeneous H ingestion into the He shell in pre-supernovae. Two of the seven putative nova grains with {sup 30}Si excesses and {sup 29}Si depletions show lower-than-solar {sup 34}S/{sup 32}S ratios that cannot be explained by classical nova nucleosynthetic models. We discuss these signatures within the CCSN scenario. For the remaining five putative nova grains, both nova and supernova origins are viable because explosive H burning in the two stellar sites could result in quite similar proton-capture isotopic signatures. Three of the grains are sub-type AB grains that are also {sup 13}C enriched, but have a range of higher {sup 14}N/{sup 15}N. We found that {sup 15}N-enriched AB grains (∼50 < {sup 14}N/{sup 15}N < ∼100) have distinctive isotopic signatures compared to putative nova grains, such as higher {sup 14}N/{sup 15}N, lower {sup 26}Al/{sup 27}Al, and lack of {sup 30}Si excess, indicating weaker proton-capture nucleosynthetic environments.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Proton dominance in the 2{sub 2}{sup +}{yields}0{sub 1}{sup +} transition of N=Z{+-}2 nuclei around {sup 28}Si
E2 transitions in {sup 30}Si are investigated in relation to intrinsic deformations based on a method of antisymmetrized molecular dynamics. By comparing E2 transition strengths in the mirror nuclei {sup 30}Si and {sup 30}S, transition matrix amplitudes M{sub p} and M{sub n} for protons and neutrons are discussed in mirror analysis. Particular attention is paid to the M{sub n}/M{sub p} ratio in the transition from the 2{sub 2}{sup +} state to the 0{sub 1}{sup +} state. The M{sub n}/M{sub p} ratio in {sup 26}Mg and {sup 26}Si is also investigated. It is found that the proton dominance in the transition 2{sub 2}{sup +}{yields}0{sub 1}{sup +} in {sup 30}Si and {sup 26}Si originates in the oblate trend of the Z=14 proton structure.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Epitaxially Grown Monoisotopic Si, Ge, and Si{sub 1–x}Ge{sub x} Alloy Layers: Production and Some Properties
The technology of the growth of Si, Ge, and Si{sub 1–x}Ge{sub x} layers by molecular-beam epitaxy with the use of a sublimation source of monoisotopic {sup 30}Si or {sup 28}Si and/or gas sources of monogermane {sup 74}GeH{sub 4} is demonstrated. All of the epitaxial layers are of high crystal quality. The secondary-ion mass spectroscopy data and Raman data suggest the high isotopic purity and structural perfection of the {sup 30}Si, {sup 28}Si, {sup 74}Ge, and {sup 30}Si{sub 1–x}{sup 74}Ge{sub x} layers. The {sup 30}Si layers doped with Er exhibit an efficient photoluminescence signal.
36 MATERIALS SCIENCE↗
Evidence for quasifission in the sub-barrier reaction of {sup 30}Si+{sup 238}U
Fragment mass distributions for fission after full momentum transfer were measured for the {sup 30}Si+{sup 238}U reaction at bombarding energies around the Coulomb barrier. At energies above the Bass barrier, the mass distributions were Gaussian with mass symmetry. An asymmetric fission channel with mass A{sub L}/A{sub H} {approx_equal} 90/178 emerged at the sub-barrier energies, where competition between fusion and quasifission was suggested from the evaporation residue (ER) cross section produced in the fusion {sup 30}Si+{sup 238}U. We thus conclude the asymmetric channel is attributed to quasifission. It was supported by a model calculation using the Langevin equation to give the fragment mass distribution, where fusion-fission and quasifission were separated. The observed mass asymmetry for quasifission as well as the calculation is significantly smaller than those observed in actinide targets bombarded with heavier projectiles, which suggests that the system {sup 30}Si+{sup 238}U approaches the shape of the compound nucleus before disintegrating as quasifission.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Fourier transform infrared identification of the ν{sub 5}(σ{sub u}) fundamental of SiC{sub 5}Si
The Fourier transform infrared spectrum of SiC{sub 5}Si was observed by trapping the vapor from the Nd:YAG laser ablation of sintered Si/C rods in solid Ar at ∼20 K. Measurements of {sup 13}C and {sup 29,30}Si isotopic shifts have enabled the identification of the ν{sub 5}(σ{sub u}) vibrational fundamental of the linear isomer of SiC{sub 5}Si at 1590.8 ± 0.2 cm{sup −1}. The results are in excellent agreement with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level. A second fundamental, ν{sub 4}(σ{sub u}), can only be tentatively identified at 2021.0 cm{sup −1}, because its isotopic shifts are overlapped by absorptions from other species.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Spins and parities of astrophysically important {sup 30}S states from {sup 28}Si({sup 3}He, n{gamma}){sup 30}S
The structure of proton-unbound {sup 30}S states strongly determines the thermonuclear {sup 29}P(p,{gamma}){sup 30}S reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I x-ray bursts. Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, levels in the E{sub x}= 4.7-4.8 MeV region, with spin and parity assignments of 3{sup +} and 2{sup +}. In recent experimental work, two candidate levels were observed with energies of 4.699 MeV and 4.814 MeV, but no experimental information on their spins and parities was obtained. We have performed an in-beam {gamma}-ray spectroscopy study of {sup 30}S with the {sup 28}Si({sup 3}He, n{gamma}){sup 30}S reaction. By constructing the decay schemes of proton-unbound states with a {gamma}-{gamma} coincidence analysis of their decay {gamma} rays, their J{sup {pi}} values were inferred from a comparison to the known decay schemes of the corresponding mirror states in {sup 30}Si. For the two aforementioned states, our results strongly corroborate the spin-parity assignments assumed in recent evaluations of the {sup 29}P(p,{gamma}){sup 30}S reaction rate.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Beyond 30% Conversion Efficiency in Silicon Solar Cells: A Numerical Demonstration
We demonstrate through precise numerical simulations the possibility of flexible, thin-film solar cells, consisting of crystalline silicon, to achieve power conversion efficiency of 31%. Our optimized photonic crystal architecture consists of a 15 μm thick cell patterned with inverted micro-pyramids with lattice spacing comparable to the wavelength of near-infrared light, enabling strong wave-interference based light trapping and absorption. Unlike previous photonic crystal designs, photogenerated charge carrier flow is guided to a grid of interdigitated back contacts with optimized geometry to minimize Auger recombination losses due to lateral current flow. Front and back surface fields provided by optimized Gaussian doping profiles are shown to play a vital role in enhancing surface passivation. We carefully delineate the drop in power conversion efficiency when surface recombination velocities exceed 100 cm/s and the doping profiles deviate from prescribed values. These results are obtained by exact numerical simulation of Maxwell’s wave equations for light propagation throughout the cell architecture and a state-of-the-art model for charge carrier transport and Auger recombination.
14 SOLAR ENERGY↗
Design and testing of microfabricated surgical tools for large animal probe insertion
Neural probes provide therapeutic stimulation for neuropsychiatric disorders or record neural activity to investigate the workings of the brain. Researchers utilize 6 mm long temporary silicon stiffeners attached with biodissolvable adhesive to insert flexible neural probes into rat brains, but increasing the probe length fivefold makes inserting large animal probes a significant challenge because of an increased potential for buckling. This study compared the insertion success rates of 6 mm and 30 mm long silicon stiffeners that were 80 μm wide and 30 μm thick, and ascertained the material thickness and modulus of elasticity that would provide successful insertion for a 30 mm probe. Using a microdrive, stiffeners were inserted into an agarose brain phantom at controlled insertion speeds while being video-recorded. Twenty-five percent of the 30 mm silicon stiffeners fully inserted at speeds approximately four times higher than the target rate of 0.13 mm/s, while 100 percent of the 6 mm silicon stiffeners inserted successfully at target speed. Critical buckling loads (P cr ) were calculated for the 6 mm and 30 mm silicon stiffeners, and for 30 mm diamond and tungsten stiffeners, with thicknesses varying from 30-80 μm. Increasing the thickness of the material by 10 μm, 20 μm and 30 μm improved the P cr by 2.4, 4.7 and 8.2 times, respectively, independent of the material, and substituting diamond for silicon multiplied the buckling capacity by 5.0 times. Stiffeners made of silicon for large animal probe insertion are not strong enough to withstand buckling upon insertion without a significant increase in thickness. Replacing silicon with diamond and increasing the thickness of the stiffener to 50 μm would afford a stiffener with the same P cr capacity as the 6 mm silicon stiffener that had a 100 percent insertion success rate. Experiments should continue with diamond to determine a minimum thickness that will ensure successful insertions and provide an adequate margin of safety.
42 ENGINEERING↗