Recurrent SI super plus -SI super minus impulse pairs and shock structure in M-region beams.
Worldwide positive-negative impulse pair observed on geomagnetic records found to be recurrent and associated with M-region disturbances
M-REGION↗
SEARCH · Engineering Papers
Results for “SI”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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He and Ne cross sections in natural Mg, Al, and Si targets and radionuclide cross sections in natural Si, Ca, Ti, and Fe targets bombarded with 14- to 45-Mev protons.
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Walton, J. R.↗
Field strength degradation in Si-SiO2-polycrystalline Si structures
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Mattauch, R. J.↗
Chromospheric oscillations observed with OSO 8. I - Basic measurements and analytical methods. II - Average power spectra for Si II. III - Average phase spectra for Si II
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White, O. R.↗
Laboratory characterization of direct readout Si:Sb and Si:Ga infrared detector arrays
Highlights of recent results obtained at Ames Research Center in performance evaluations of infrared detector arrays are presented. Antimony- and gallium-doped silicon direct readout 58x62 element hybrid devices from Ames' ongoing detector technology development program are described. The observed characteristics meet most of the performance goals specified by the Space Infrared Telescope Facility (SIRTF) instrument teams and compare favorably with the best performance reported for discrete non-integrating extrinsic silicon detectors. Initial results of radiation environment testing are reported, and non-ideal behavior demonstrated by these test devices is discussed.
Mckelvey, Mark E.↗
Materials Data on Si by Materials Project
Si is Clathrate-like structured and crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. there are ten inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are three shorter (2.36 Å) and one longer (2.38 Å) Si–Si bond lengths. In the second Si site, Si is bonded to four Si atoms to form a mixture of edge and corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.36–2.44 Å. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.33 Å) and one longer (2.36 Å) Si–Si bond lengths. In the fourth Si site, Si is bonded to four Si atoms to form a mixture of edge and corner-sharing SiSi4 trigonal pyramids. There are a spread of Si–Si bond distances ranging from 2.31–2.36 Å. In the fifth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.65 Å. In the sixth Si site, Si is bonded to four equivalent Si atoms to form corner-sharing SiSi4 tetrahedra. In the seventh Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.40 Å) and one longer (2.48 Å) Si–Si bond lengths. In the eighth Si site, Si is bonded to four Si atoms to form a mixture of distorted edge and corner-sharing SiSi4 trigonal pyramids. The Si–Si bond length is 2.39 Å. In the ninth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.41 Å) and one longer (2.43 Å) Si–Si bond lengths. In the tenth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Clathrate-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are nine inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.35–2.40 Å. In the second Si site, Si is bonded to four Si atoms to form a mixture of edge and corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.33–2.39 Å. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.33 Å) and three longer (2.35 Å) Si–Si bond lengths. In the fourth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.38–2.48 Å. In the fifth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.38 Å. In the sixth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. Both Si–Si bond lengths are 2.32 Å. In the seventh Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.41 Å. In the eighth Si site, Si is bonded to four Si atoms to form a mixture of edge and corner-sharing SiSi4 tetrahedra. In the ninth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is alpha Samarium structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are eight inequivalent Si sites. In the first Si site, Si is bonded to twelve Si atoms to form a mixture of corner, edge, and face-sharing SiSi12 cuboctahedra. There are six shorter (2.69 Å) and six longer (2.76 Å) Si–Si bond lengths. In the second Si site, Si is bonded to twelve Si atoms to form a mixture of corner, edge, and face-sharing SiSi12 cuboctahedra. There are a spread of Si–Si bond distances ranging from 2.69–2.77 Å. In the third Si site, Si is bonded to twelve Si atoms to form a mixture of corner, edge, and face-sharing SiSi12 cuboctahedra. All Si–Si bond lengths are 2.69 Å. In the fourth Si site, Si is bonded to twelve Si atoms to form SiSi12 cuboctahedra that share corners with fifteen SiSi16 cuboctahedra, edges with twenty-one SiSi16 cuboctahedra, and faces with nineteen SiSi12 cuboctahedra. There are a spread of Si–Si bond distances ranging from 2.69–2.77 Å. In the fifth Si site, Si is bonded to twelve Si atoms to form a mixture of corner, edge, and face-sharing SiSi12 cuboctahedra. There are six shorter (2.69 Å) and three longer (2.76 Å) Si–Si bond lengths. In the sixth Si site, Si is bonded to twelve Si atoms to form SiSi12 cuboctahedra that share corners with twenty-three SiSi16 cuboctahedra, edges with sixteen SiSi16 cuboctahedra, and faces with twenty-three SiSi12 cuboctahedra. There are six shorter (2.69 Å) and three longer (2.76 Å) Si–Si bond lengths. In the seventh Si site, Si is bonded to twelve Si atoms to form SiSi12 cuboctahedra that share corners with twenty SiSi16 cuboctahedra, edges with nineteen SiSi12 cuboctahedra, and faces with twenty-two SiSi12 cuboctahedra. There are six shorter (2.69 Å) and three longer (2.77 Å) Si–Si bond lengths. In the eighth Si site, Si is bonded to sixteen Si atoms to form SiSi16 cuboctahedra that share corners with twenty-five SiSi12 cuboctahedra, edges with twenty-one SiSi16 cuboctahedra, and faces with thirty-five SiSi16 cuboctahedra. There are a spread of Si–Si bond distances ranging from 2.69–5.37 Å.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent Si sites. In the first Si site, Si is bonded in a distorted pentagonal planar geometry to five Si atoms. There are a spread of Si–Si bond distances ranging from 2.34–2.67 Å. In the second Si site, Si is bonded in a 4-coordinate geometry to four Si atoms. There are a spread of Si–Si bond distances ranging from 2.41–2.58 Å. In the third Si site, Si is bonded in a tetrahedral geometry to four Si atoms. There are a spread of Si–Si bond distances ranging from 2.36–2.39 Å. In the fourth Si site, Si is bonded in a 4-coordinate geometry to four Si atoms. There are one shorter (2.39 Å) and one longer (2.41 Å) Si–Si bond lengths. In the fifth Si site, Si is bonded in a 4-coordinate geometry to four Si atoms. The Si–Si bond length is 2.44 Å. In the sixth Si site, Si is bonded in a 5-coordinate geometry to five Si atoms. There are one shorter (2.37 Å) and one longer (2.78 Å) Si–Si bond lengths. In the seventh Si site, Si is bonded in a 3-coordinate geometry to five Si atoms. The Si–Si bond length is 2.76 Å. In the eighth Si site, Si is bonded in a 4-coordinate geometry to five Si atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Clathrate-like structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are eight inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.34–2.41 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.32–2.37 Å. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.31 Å. In the fourth Si site, Si is bonded to four Si atoms to form a mixture of corner and edge-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.41–2.46 Å. In the fifth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.31 Å. In the sixth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.33 Å. In the seventh Si site, Si is bonded to four Si atoms to form a mixture of distorted corner and edge-sharing SiSi4 tetrahedra. There are one shorter (2.41 Å) and two longer (2.46 Å) Si–Si bond lengths. In the eighth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Clathrate-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are seven inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.37–2.40 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.34 Å) and one longer (2.37 Å) Si–Si bond lengths. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.37 Å. In the fourth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.33 Å. In the fifth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.40 Å. In the sixth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. Both Si–Si bond lengths are 2.37 Å. In the seventh Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra.
36 MATERIALS SCIENCE↗
In-situ hydrogen microstructural characterization of Si heterojunction passivation: Addressing V OC degradation and mitigation pathways
Si heterojunction (SHJ) solar cells have demonstrated record efficiency >27%, approaching the theoretical limit of ≈ 29%, primarily due to best surface/interface defect passivation provided by deposited thin layers of hydrogenated amorphous silicon (a-Si:H). Such excellent surface/interface passivation reduces recombination loss and result in >100 mV improvement of cell open circuit voltage (V OC ) to ≈ 750 mV, thus the cell efficiency. However, fielded SHJ modules exhibit loss of V OC and hence efficiency over time in years, presumably due to degradation related to a-Si:H layers. This adversely affects the technology’s market acceptance, and levelized cost of energy (LCOE). It is hypothesized that the origin of a-Si:H degradation is somehow related to the presence of weak Si–Si bonds and hydrogen in a-Si:H films. The objective of this project is to test this hypothesis by directly measuring chemical and structural changes occurring within SHJ component layers and solar cells. This is achieved by developing an innovative in-situ Fourier transform infrared (FTIR) spectrometry apparatus to monitor hydrogen microstructural changes occurring within amorphous silicon and decipher hydrogen evolution kinetics over time when samples are exposed to heat and/or light stress. These in-situ measured hydrogen microstructural changes are correlated to the changes in effective minority carrier lifetime (τ eff ), implied V OC (iV OC ), surface recombination velocity (S), and cell V OC . These mechanistic understandings will provide critical guidance to mitigate the V OC -driven degradation of SHJ solar cell performance. Passivation optimization and degradation analysis of individual SHJ component structures were achieved through systematic deposition of three symmetric structures and the completed SHJ solar cell structure. The three symmetric structures used were intrinsic a-Si:H [(i)a-Si:H] layers in a bilayer structure, intrinsic and p-type doped stacked layers [(i-p)a-Si:H] representing the front heterojunction in the SHJ cell, and intrinsic and n-typed doped stacked layers [(i-n)a-Si:H] representing the back-side back surface field (BSF) in the SHJ cell. State-of-the-art passivation qualities are demonstrated by a champion iV OC of 740 mV for the (i)a-Si:H layers, and the (i-n)a-Si:H symmetric structure. A 725 mV iV OC is observed for the (i-p)a-Si:H symmetric structure. These symmetric passivated SHJ component structures were subsequently subjected to different accelerated lifetime (ALT) stressors to identify which conditions contribute the most to iV OC degradation. Degradation of the thin (10 nm) (i)a-Si:H passivation layers without any additional overlying layers is minimal; complexity of this study arises due to unavoidable surface oxidation of (i)a-Si:H layer during most of the stress application, which is likely irrelevant for a full SHJ cell configuration with overlying protective layers. The iV OC degradation of symmetric structures is found to occur primarily at the (i-p)a-Si:H passivation stack under dark heat stress with associated hydrogen loss from the (p)a-Si:H layer. An activation energy for increase in S (defect creation) of 0.65 eV can be correlated to the activation energy of ≈ 0.4 eV for hydrogen loss from the (i-p)a-Si:H stack. This also suggests the presence of weakly bonded hydrogen in the (p)a-Si:H films, which effuses out of the film stack at such low activation energy. When light and heat stress are applied together, similar hydrogen loss from (i-p)a-Si:H stack is observed, however, does not appreciably degrade iV OC or increase S. This is an important result and departure from direct correlation between hydrogen loss and defect creation. This perhaps indicates additional defect chemistries or annealing that might be occurring in the presence of light requiring further detailed defect measurements. The full SHJ cell structure used for this project is depicted in Fig.1(d). SHJ cells with an initial V OC ≈ 700 mV were fabricated and subjected to similar ALT stress conditions. Cell V OC is found to degrade the most under dark heat stress and is confirmed by observed hydrogen migration out of the (i-p)a-Si:H stack. However, hydrogen cannot escape from the cell stack, it accumulates near the (p)a-Si:H/ITO contact interface, where ITO acts as a barrier preventing hydrogen loss. Furthermore, light-heat combined stress does not degrade V OC appreciably, confirming the occurrence of a defect annealing process.
14 SOLAR ENERGY↗
Materials Data on Si by Materials Project
Si is Theoretical Carbon Structure-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.35–2.39 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.40 Å) and one longer (2.42 Å) Si–Si bond lengths. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.32 Å) and two longer (2.35 Å) Si–Si bond lengths. In the fourth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. Both Si–Si bond lengths are 2.35 Å.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Theoretical Carbon Structure-like structured and crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are four inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form a mixture of edge and corner-sharing SiSi4 tetrahedra. There are one shorter (2.34 Å) and three longer (2.38 Å) Si–Si bond lengths. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are one shorter (2.35 Å) and three longer (2.39 Å) Si–Si bond lengths. In the third Si site, Si is bonded to four equivalent Si atoms to form corner-sharing SiSi4 tetrahedra. In the fourth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.40 Å.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Theoretical Carbon Structure-like structured and crystallizes in the cubic I-43m space group. The structure is three-dimensional. there are four inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.35–2.42 Å. In the second Si site, Si is bonded to four equivalent Si atoms to form distorted corner-sharing SiSi4 tetrahedra. In the third Si site, Si is bonded to four equivalent Si atoms to form corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.37 Å. In the fourth Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra.
36 MATERIALS SCIENCE↗
Atomistic modeling of interface strengthening in Al-Si eutectic alloys
Al-Si cast alloys are usually composed of α-Al and Al-Si eutectic. Si flakes and Al matrix generally hold cube-on-cube orientation relationship with the primary interface (111) Al ∥(111) Si . Extensive experimental studies demonstrated that Si flakes cannot significantly improve mechanical properties of Al-Si cast alloys. We hypothesize that the weak strengthening effect associated with Si flakes might be attributed to thermomechanical properties of Al-Si interfaces besides their morphologies. To characterize Al-Si interfaces with a large lattice mismatch (> 30%), we proposed the quasi-coincident site lattice (Q-CSL) as reference lattice, and demonstrated that the Q-CSL Al-Si coherent interface has three characteristic coherent structures, one stable and low energy structure and two metastable and high energy structures. The translation vectors for the same type of coherent Q-CSL structures are consistent with three displacement shift complete (DSC) vectors. The two metastable structures can be obtained by shifting the low energy structure with three partial DSC vectors. Semi-coherent interface is composed of the low energy Q-CSL patches and three sets of interface misfit dislocations with Burgers vectors same as the DSC vectors. Atomistic simulations revealed that Al-Si interface exhibits low shear resistance. Ideal shear strength of the Q-CSL coherent interface is 110 MPa and semi-coherent interface is 20 MPa. The low shear resistance is attributed to the glide of interface misfit dislocations. Al-Si interface also exhibits low formation and migration energies of point defects. Owing to low shear strength and low formation and migration energies of point defects, interface sliding or shear readily happen under mechanical loading or during dislocation-interface interactions. Lattice dislocations can cross slip onto or climb along Al-Si interfaces. These reactions decrease the number of accumulated dislocation loops around Si flakes and promote nucleation and emission of lattice dislocations from Al-Si interfaces to matrix, consequently reduce the repulsive force on approaching dislocations and weaken Si flakes strengthening effect. In situ tension and compression tests in a scanning electron microscope reveal relatively weak strengthening effect due to Si flakes, consistent with the computed dislocation interaction with interfaces and shear behavior of interfaces.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are three inequivalent Si sites. In the first Si site, Si is bonded in a tetrahedral geometry to four equivalent Si atoms. All Si–Si bond lengths are 2.82 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. All Si–Si bond lengths are 2.32 Å. In the third Si site, Si is bonded in a distorted see-saw-like geometry to four Si atoms. There are two shorter (2.34 Å) and one longer (2.44 Å) Si–Si bond lengths.
36 MATERIALS SCIENCE↗
Materials Data on Si by Materials Project
Si is Theoretical Carbon Structure-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent Si sites. In the first Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are a spread of Si–Si bond distances ranging from 2.35–2.39 Å. In the second Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. There are two shorter (2.36 Å) and one longer (2.39 Å) Si–Si bond lengths. In the third Si site, Si is bonded to four Si atoms to form corner-sharing SiSi4 tetrahedra. The Si–Si bond length is 2.37 Å.
36 MATERIALS SCIENCE↗