Search results for "silicon"
showing 10 items of 1391 documents
Interstitial carbon defects in silicon. A quantum mechanical characterization through the infrared and Raman spectra.
2021
The infrared (IR) and Raman spectra of eight substitutional carbon defects in silicon are computed at the quantum mechanical level by using a periodic supercell approach based on hybrid functionals, an all electron Gaussian type basis set and the CRYSTAL code. The single substitutional C s case and its combination with a vacancy (C s V and C s SiV) are considered first. The progressive saturation of the four bonds of a Si atom with C is then examined. The last set of defects consists of a chain of adjacent carbon atoms C s i , with i = 1-3. The simple substitutional case, C s , is the common first member of the three sets. All these defects show important, very characteristic features in th…
Grafting Silicone at Room Temperature—a Transparent, Scratch-resistant Nonstick Molecular Coating
2020
Silicones are usually considered to be inert and, thus, not reactive with surfaces. Here we show that the most common silicone, methyl-terminated polydimethylsiloxane, spontaneously and stably bonds on glass-and any other material with silicon oxide surface chemistry-even at room temperature. As a result, a 2-5 nm thick and transparent coating, which shows extraordinary nonstick properties toward polar and nonpolar liquids, ice, and even super glue, is formed. Ten microliter drops of various liquids slide off a coated glass when the sample is inclined by less than 10°. Ice adhesion strength on a coated glass is only 2.7 ± 0.6 kPa, that is, more than 98% less than ice adhesion on an uncoated…
A study of densified biochar as carbon source in the silicon and ferrosilicon production
2019
Abstract Biochar pellets were investigated as renewable reducing agents in substitution of coal and coke in the silicon and ferrosilicon production, where a high reactivity, good mechanical properties and low feedstock costs are appreciated. The usage of pyrolysis oil as binder was investigated as way to improve the quality of the pellets. Norway spruce biochar produced at 500, 800 and 1100 °C, was pelletized blended with pyrolysis oil and lignosulphonate. A second heat treatment was carried out at the same temperatures to evaluate the interaction between biochar and pyrolysis oil and to imitate the thermal stability of the pellets when used in a furnace. Density, tensile strength and mecha…
Research Regarding Uniaxial Tensile Strength of Nylon Woven Fabrics, Coated and Uncoated with Silicone
2019
Properties of woven fabrics used to make airbag cushions are influenced by a lot of factors: the nature of raw materials, woven fabric geometry and density, technological parameters of the weaving operation and finishing. The main purpose of this research paper is to find the values of three mechanical parameters – tensile strain, tensile stress and specific modulus – according to the type of samples and test direction on the testing stand. To obtain woven fabric samples were used polyamide 6-6 polyfilament yarns (nylon), silicone coated and uncoated fabric. Testing procedure and samples preparation were done following the standard EN ISO 13934-1:1999. Test results and graphs show that, we …
Light absorption and electrical transport in Si:O alloys for photovoltaics
2010
Thin films (100-500 nm) of the Si:O alloy have been systematically characterized in the optical absorption and electrical transport behavior, by varying the Si content from 43 up to 100 at. %. Magnetron sputtering or plasma enhanced chemical vapor deposition have been used for the Si:O alloy deposition, followed by annealing up to 1250 °C. Boron implantation (30 keV, 3-30× 1014 B/cm2) on selected samples was performed to vary the electrical sheet resistance measured by the four-point collinear probe method. Transmittance and reflectance spectra have been extracted and combined to estimate the absorption spectra and the optical band gap, by means of the Tauc analysis. Raman spectroscopy was …
Low-frequency band gap in cross-like holey phononic crystal strip
2018
International audience; A silicon-based cross-like holey phononic crystal (PnC) strip is proposed for the control of elastic waves in the field of micro-electro-mechanical systems (MEMS). The goal is to obtain a broad bandgap at low frequencies with a lightweight structure. In this respect, the effects of varying the in-plane and the out-of-plane geometry parameters are discussed. After design, a gap-to-midgap ratio of 47% is obtained with an intermediate filling fraction of the solid material and a small thickness of the strip. The band gap can be moved to an extremely low frequency range while keeping the strip significantly smaller than previously reported PnC strips. The transmission pr…
The use of non-cavitating coupling fluids for intensifying sonoelectrochemical processes
2020
Abstract For the first time, we have investigated the beneficial effects of non-cavitating coupling fluids and their moderate overpressures in enhancing mass-transfer and acoustic energy transfer in a double cell micro-sonoreactor. Silicon and engine oils of different viscosities were used as non-cavitating coupling fluids. A formulated monoethylene glycol (FMG), which is a regular cooling fluid, was also used as reference. It was found that silicon oil yielded a maximum acoustic energy transfer (3.05 W/cm2) from the double jacketed cell to the inner cell volume, at 1 bar of coupling fluid overpressure which was 2.5 times higher than the regular FMG cooling fluid. It was also found that the…
Photoemission study of the reactivity of barium towards SiOx thermal films
2011
Abstract Barium was deposited at room temperature on a thermal silicon oxide layer and the interfacial reaction was monitored by synchrotron induced photoemission (both core level and valence band). The first step of the growth consists of an interfacial reaction which leads to the formation of an interfacial silicate layer. The next step consists in formation of barium oxide while metallic barium occurs subsequently. The deposit can be also homogenized by annealing above 575 K. This results in the formation of several layers of silicate by consumption of silicon oxide. In the case of fractional coverage, subsequent annealing at 975 K induces the decomposition of barium silicate. However, s…
Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications
2020
AbstractThe application of molybdenum oxide in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells in the role of hole selective contact. For modeling-based optimization of such contact, knowledge of the molybdenum oxide defect density of states (DOS) is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of defects related to oxygen-vacancy and of polaron is supported by the results of our opto-electrical characterizations along with the evaluation of previous observations. As part…
Elaboration and characterization of barium silicate thin films.
2008
International audience; Room temperature depositions of barium on a thermal silicon oxide layer were performed in ultra high vacuum (UHV). In-situ X-ray photoelectron spectroscopy (XPS) analyses were carried out as well after exposure to air as after subsequent annealings. These analyses were ex-situ completed by secondary ion mass spectrometry (SIMS) profiles and transmission electron microscopy (TEM) cross-sectional images. The results showed that after air exposure, the barium went carbonated. Annealing at sufficient temperature permitted to decompose the carbonate to benefit of a barium silicate. The silicate layer was formed by interdiffusion of barium with the initial SiO2 layer.