Epitaxial Electrodeposition of Optically Transparent Hole-Conducting CuI on n-Si(111)
Not provided.
Chemistry↗
SEARCH · Search NASA
Results for “N-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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Interfacial Reactivity of Silicon Electrodes: Impact of Electrolyte Solvent and Presence of Conductive Carbon
Silicon (Si) is a promising high-capacity material for lithium-ion batteries; however, its limited reversibility hinders commercial adoption. Approaches such as particle and crystallite size reduction, introduction of conductive carbon, and use of different electrolyte solvents have been explored to overcome these electrochemical limitations. Herein, operando isothermal microcalorimetry (IMC) is used to probe the influence of silicon particle size, electrode composition, and electrolyte additives fluoroethylene carbonate and vinylene carbonate on the heat flow during silicon lithiation. In this work, the IMC data are complemented by X-ray photoelectron and Raman spectroscopies to elucidate differences in solid electrolyte interphase (SEI) composition. Nanosized (~50 nm, n-Si) and micrometer-sized (~4 μm, μ-Si) silicon electrodes are formulated with and without amorphous carbon and electrochemically lithiated in ethylene carbonate (EC), fluoroethylene carbonate (FEC), or vinylene carbonate (VC) based electrolytes. Notably, n-Si electrodes generate 53–61% more normalized heat relative to their μ-Si counterparts, consistent with increased surface area and electrode/electrolyte reactivity. Introduction of amorphous carbon significantly alters the heat flow profile where multiple exothermic peaks and increased normalized heat dissipation are observed for all electrolyte types. Notably, the VC-containing electrolyte demonstrates the greatest normalized heat dissipation of the electrode compositions tested showing as much as a 50% increase compared to the EC or FEC counterparts. The results are relevant to the understanding of silicon negative electrode function in the presence of electrolyte additives and provide insight relative to silicon containing cell reactivity and safety.
25 ENERGY STORAGE↗
Conformal SnO x heterojunction coatings for stabilized photoelectrochemical water oxidation using arrays of silicon microcones
A protective tin oxide layer formed by atomic-layer deposition limits surface recombination at n-Si surfaces and produces ∼620 mV of photovoltage on planar n-Si photoanodes. The layer conformally coats structures such as Si microcone arrays.
Moreno-Hernandez, Ivan A.↗
Reverse phonon thermal flux from an applied electric field
In the phenomenon known as electron drag, a phonon thermal flux is established in a conducting crystal by an electric field applied under isothermal conditions through directed transfer of quasimomentum from the electronic charge current to the phonon subsystem. Prior understanding of this phenomenon involves a thermal current composed of low-frequency acoustic phonons that is in the same direction as the charge current. This results in an increase of the Peltier thermopower. Here, we show that it is also possible to establish a phonon thermal current that is in the opposite direction to the charge current, which we refer to as a reverse phonon thermal flux. We demonstrate this behavior both through a simple qualitative model and through first-principles calculations performed for three materials: p-type 𝜃-TaN, n-type BAs, and n-type Si. The reverse phonon flux is shown to arise through intervalley electron-phonon scattering processes involving high-frequency acoustic phonons. Unlike n-BAs and n-Si, the combined features in the band structure and phonon dispersions of p-type 𝜃-TaN promote a particularly large reverse phonon thermal flux comparable in magnitude to the oppositely directed thermal flux from low-frequency phonons. Finally, this work highlights a previously unrecognized behavior in the coupled electron-phonon system and advances our understanding of the rich physics of transport in solids.
lattice dynamics↗
Exploiting Fixed Charge at Selective Contacts for Silicon Photovoltaics
The goal of this work was to examine and exploit fixed interface charges in ultra-thin (0-3 nm thickness) tunnel dielectric layers sandwiched between silicon and selective contact metal oxides (molybdenum oxide, MoO x , titanium oxide, TiO 2 ). Specifically, the interface fixed charge was varied by changing processing conditions and materials over a wide range and the effect on the current-voltage behavior and the Schottky barrier height was quantified. In budget period 1 (year 1), the objective was to grow aluminum oxide tunnel layers with quantified fixed charge over a range of ~1E12 to ~-2E12 cm -2 and combine these with MoO x and TiO 2 layers on Czochralsi (CZ) mono p- and n-Si, respectively. We sought conditions that maximize fixed charge and minimize Schottky barrier height to MoO x contacts to p-Si. This objective, along with investigating the effects of silicon surface terminations, occupied the majority of the project timeline (Q1-Q8) due to complications with high specific contact resistivity values. In the last two quarters of the project period, the objective was to insert HfO2 layers between Si and aluminum oxide layers to quench the fixed charge for layers with otherwise identical thermal history. Another objective was to lower the barrier height at TiO 2 -based contacts on n-type Si, but that was never investigated completely.
14 SOLAR ENERGY↗
Development of ~25% Efficient Double Side Screen Printed Poly-Si/SiO x Passivated Contact Solar Cells
This program aims to overcome these challenges and develop high-efficiency (24-25%) double-side (DS) TOPCon solar cells by maximizing passivation on both sides while mitigating light absorption losses. To achieve this, the program will implement either thin (≤ 20 nm) homogeneous n-TOPCon on the entire front surface or selective area thick (≥ 100 nm) n-TOPCon only underneath the front metal contact with ~90% field region composed of dielectric passivated textured n-Si in between the poly-Si/metal grid. The rear side will feature ~250 nm-thick full-area planar p-TOPCon, which functions as the rear junction. Recombination and parasitic absorption losses in the front and rear TOPCon layers will be minimized by tailoring their doping profiles and thickness. Additionally, the device performance will be further enhanced through the optimization of bulk parameters, including the carrier lifetime, resistivity, and thickness of the n-type Si absorber. Finally, advanced metallization techniques, such as fine-line printing, and floating busbar or busbar-less designs, will be employed to reduce recombination, resistive, and optical losses. The program started with the development of a technology roadmap for DS-TOPCon cells to achieve target efficiency.
14 SOLAR ENERGY↗
Microcrystalline silicon growth for heterojunction solar cells
A single source of evaporation with B mixed with highly doped Si is used instead of the coevaporation of separate Si and B sources to reduce possible carbon contamination. The results of both the heterojunction or heteroface structures, however, are similar when evaporation is used. The best Voc of the heterojunction is about 460mV and no improvement in Voc in the heteroface structure is observed. Slight Voc degradation occurred. A study of the p m-Si/p c-Si structure showed a negative Voc in many cases. The interface properties between the two materials are such that instead of repelling minority carriers from the substrate carrier, collection actually occurred. Another study of cells made in the part of substrates not covered by n-Si results in performance lower than the controls. This indicates possible substrate degradation in the process.
Iles, P. A.↗
Optical and electrical characterizations of laser-chemical-vapor-deposited aluminum oxynitride films
Composition-dependent optical and electrical properties of L-CVD (Al2O3)1-c-(AlN)c composite films are examined. The optical properties exhibit a continuous change from Al2O3 to AlN with increasing value of the composition parameter c from zero to one. There is a critical concentration value of about 0.3 below and above which Al2O3- and AlN-like optical properties are observed. The impurity absorption regions are 5.1-6.7 eV for Al2O32 and 4.6-6.0 for AlN, while the energy gap is about 6.7 eV for Al2O3 and 6.0 eV for AlN. The electrical properties of Al-insulator n-Si MIS structures display externally programmable states when bulk-controlled electron emission occurs from the traps. In the high-field region a persistent polarization field is established within the insulator. C-V characteristics of the samples are more sensitive to the concentration factor c than the I-V characteristics. A large clockwise hysteresis is observed for AlN, but a smaller counterclockwise one is observed for Al2O3.
Demiryont, H.↗
Electrical and Optical Property of Ferroelectric BaTiO3:Eu
We studied various electrical and optical properties of Europium (1 atomic %) incorporated BaTiO3 film on n-Si(100) substrate. The thin film structure was analyzed by X-ray diffraction. Film thickness and optical refractive index were measured with an ellipsometer. P-E hysteresis measurement shows the remnant polarization of 37 micro C/sq cm in BaTiO3:Eu film. C-V measurements on the pure BaTiO3 film show recovery of capacitance across sweeping voltage ranges with a narrow transition zone due to the polarization change. On the other hand, C-V and I-V measurements on the BaTiO3:Eu film show that Europium incorporation increases positively charged states in the BaTiO3 layer such that BaTiO3:Eu/n-Si interface behaves like a leaky p-n junction.
Park, Yeonjoon↗
Mechanism of Hydrogen Passivation in Passivated Contact Si Solar Cells
In this abstract, we discuss the mechanism of hydrogen passivation on symmetrical n-Si/ultra-thin SiO2/polySi structures. The hydrogen was introduced from different hydrogen-containing dielectric layers (AlOx:H and SiNx:H and their stacks), as well as by forming gas anneal (FGA). The effusion of hydrogen both from the dielectric layers and in the underlying poly-Si was explored using a quadrupole mass spectrometer (QMS) and FTIR spectroscopy. We show that the strength of hydrogen bonds depend on the deposition technique as well as hydrogenation mechanism. While a PECVD SiNx:H loses hydrogen at a peak temperature of ~450 degrees C, LPCVD SiNx:H, although having less hydrogen compared to PECVD, effuses at a peak temperature of ~850 degrees C. This becomes important to maintain passivation of passivated contacts after firing of metal contacts at high temperatures. On the other hand, it has been observed that SiNx:H provides larger amount of hydrogen to poly-Si after FGA compared to FGA treated AlOx:H, which acts as a capping layer and helps in retaining the hydrogen up to higher temperatures.
hydrogen bonding configuration↗
Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Si4+ is bonded to four equivalent N3- atoms to form corner-sharing SiN4 tetrahedra. All Si–N bond lengths are 1.76 Å. N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si3N4 by Materials Project
Si3N4 is Hausmannite structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to six equivalent N3- atoms to form SiN6 octahedra that share corners with six equivalent SiN4 tetrahedra and edges with six equivalent SiN6 octahedra. All Si–N bond lengths are 1.89 Å. In the second Si4+ site, Si4+ is bonded to four equivalent N3- atoms to form corner-sharing SiN4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. All Si–N bond lengths are 1.79 Å. N3- is bonded in a distorted rectangular see-saw-like geometry to four Si4+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the trigonal P31c space group. The structure is three-dimensional. there are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four N3- atoms to form corner-sharing SiN4 tetrahedra. There are a spread of Si–N bond distances ranging from 1.74–1.76 Å. In the second Si4+ site, Si4+ is bonded to four N3- atoms to form corner-sharing SiN4 tetrahedra. There are a spread of Si–N bond distances ranging from 1.73–1.75 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to three Si4+ atoms. In the second N3- site, N3- is bonded in a trigonal planar geometry to three Si4+ atoms. In the third N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms. In the fourth N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Si4+ is bonded to five N3- atoms to form a mixture of edge and corner-sharing SiN5 trigonal bipyramids. There are a spread of Si–N bond distances ranging from 1.75–1.99 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a see-saw-like geometry to four equivalent Si4+ atoms. In the second N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the trigonal P31c space group. The structure is three-dimensional. there are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded in a distorted see-saw-like geometry to four N3- atoms. There are a spread of Si–N bond distances ranging from 1.79–2.12 Å. In the second Si4+ site, Si4+ is bonded to five N3- atoms to form a mixture of distorted edge and corner-sharing SiN5 trigonal bipyramids. There are a spread of Si–N bond distances ranging from 1.77–1.94 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted trigonal planar geometry to three Si4+ atoms. In the second N3- site, N3- is bonded to four Si4+ atoms to form distorted corner-sharing NSi4 trigonal pyramids. In the third N3- site, N3- is bonded in a 4-coordinate geometry to three equivalent Si4+ and one N3- atom. The N–N bond length is 1.27 Å. In the fourth N3- site, N3- is bonded in a 4-coordinate geometry to three equivalent Si4+ and one N3- atom.
36 MATERIALS SCIENCE↗
Materials Data on Si3N2 by Materials Project
Si3N2 is alpha Po structured and crystallizes in the cubic Pm-3m space group. The structure is zero-dimensional and consists of one Si3N2 cluster. Si+1.33+ is bonded in a bent 120 degrees geometry to two equivalent N2- atoms. Both Si–N bond lengths are 1.76 Å. N2- is bonded in a trigonal planar geometry to three equivalent Si+1.33+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on Si3N4 by Materials Project
Si3N4 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Si4+ is bonded to four N3- atoms to form corner-sharing SiN4 tetrahedra. There is one shorter (1.74 Å) and three longer (1.75 Å) Si–N bond length. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms. In the second N3- site, N3- is bonded in a trigonal planar geometry to three equivalent Si4+ atoms.
36 MATERIALS SCIENCE↗