Silicon Oxide Phase Research Articles

Peculiarities in XPS spectra of Sn/SiO2 layers as an effect of surface charge

X-ray photoelectron spectroscopy based on synchrotron radiation was used to investigate the composition of the observed SnO2-x/Sn:SiO2-x thin layer grown by organometallic chemical vapour deposition on single-crystalline silicon wafer with additional argon ions etching treatment. Due to the formation of a thermodynamic anomaly during in situ layer growth, an efficient oxygen exchange between silicon and tin oxide phases occurs. The present study addresses the effect of localized surface charging and its influence on the obtained XPS core level spectra. We found that due to the high electrical conductivity of metallic tin and the direct coupling of tin particles to the silicon wafer, the XPS Sn 3d5/2 core level spectrum is not affected by the surface charge compared to the highly charged dielectric silicon oxide matrix, as observed for the XPS O 1 s and Si 2p core level spectra. Our results show that the core level spectra of Si 2p and O 1 s are shifted up to 3 eV due to the presence of uncompensated positive charge on the surface of the silica matrix. These results provide insight into the influence of surface charge effects on the analysis of conductor/insulator composite materials and contribute to the application of Sn-based materials in various application concepts related to energy and surface functionalization.

Simultaneous spectral differentiation of multiple fluorophores in super-resolution imaging using a glass phase plate.

By engineering the point-spread function (PSF) of single molecules, different fluorophore species can be imaged simultaneously and distinguished by their unique PSF patterns. Here, we insert a silicon-dioxide phase plate at the Fourier plane of the detection path of a wide-field fluorescence microscope to produce distinguishable PSFs (X-PSFs) at different wavelengths. We demonstrate that the resulting PSFs can be localized spatially and spectrally using a maximum-likelihood estimation algorithm and can be utilized for hyper-spectral super-resolution microscopy of biological samples. We produced superresolution images of fixed U2OS cells using X-PSFs for dSTORM imaging with simultaneous illumination of up to three fluorophore species. The species were distinguished only by the PSF pattern. We achieved ∼21-nm lateral localization precision (FWHM) and ∼17-nm axial precision (FWHM) with an average of 1,800 - 3,500 photons per PSF and a background as high as 130 - 400 photons per pixel. The modified PSF distinguished fluorescent probes with ∼80 nm separation between spectral peaks.

The microstructure and deformation behavior of W-SiC composites via spark plasma sintering

In this paper, 0.5 wt% SiC nano particles and pure tungsten powders were thoroughly mixed using ball milling, followed by sintering the mixture using Spark Plasma Sintering (SPS) to obtain the W-0.5SiC composite material block. Then, the effect of sintering temperature on the microstructure and mechanical properties of W-0.5SiC composite was investigated. It was found that the tungsten carbide (W2C) and silicon oxide (SiO2) phases formed at the grain boundaris during the sintering process. Besides, the grain size of the composite increased with the increasing sintering temperature. To better understanding the mechanism of the grain growth, parameter fitting was proceeded based on the well-known grain growth power law. The grain growth parameters pointed out that the grain growth of the W-0.5SiC composite during the SPS process was mainly controlled by the surface diffusion. The hardness of 1800 °C sintered W-0.5SiC composite reached 342.2 ± 4.3 HV, and the compressive strength reaches 1417 ± 137 MPa. The digital image correlation technique was used during the compressive test of 1800 °C sintered W-0.5SiC composite to investigate the deformation behavior. The result indicated that the cracks tended to form at the edge of the sample or near the surface. The extension direction was almost parallel to the loading direction and went throughout the entire sample in at most 0.2 s.

Modification of Silicon Nanostructures by Cold Atmospheric Pressure Plasma Jets

Cold atmospheric plasma (CAP) jets with helium (He) and argon (Ar) plasma-forming gases were used to modify the structure, photoluminescence (PL), and electrical properties of arrays of silicon nanowires (SiNWs) with initial cross-section sizes of the order of 100 nm and length of about 7‒8 microns. The CAP source consisted of a 30 kHz voltage generator with a full power up to 5 W and the CAP treatment for 1‒5 min resulted in spattering of SiNWs’ tips followed by redeposition of silicon atoms. An increase of the silicon oxide phase and a decrease of the PL intensity were observed in the plasma processed SiNW arrays. A decrease of the free hole concentration and an increase in the free electron density were revealed in heavily boron and phosphorous doped SiNWs, respectively, as it was monitored by means of the Raman spectroscopy, considering a coupling of the light scattering by phonon and free charge carriers (Fano effect) in SiNWs. The obtained results demonstrate that the CAP treatment can be used to change the length, sharpness, luminescence intensity, and electrical properties of silicon nanowires for possible applications in optoelectronics and sensorics.

Carbon ion self–sputtering attained by sublimation of hot graphite target and controlled by pulse injection of a neon–helium gas mixture

The operation of graphite targets with an increased temperature (HT – hot target) is studied for the case of gas injection magnetron sputtering (GIMS) of: 1) diamond–like carbon (DLC), and 2) carbon–silicon carbide (C–SiC) films. A purposely–thinned graphite target with a reduced thermal conductivity is applied for DLC deposition, extending its high temperature sputtering range up to 1636 °C. For the purpose of C–SiC synthesis four sockets with a silicon carbide powder are designed within graphite target. In this approach, the C–SiC target surface can be heated up to 1443 °C due to a greater energy input from impulse plasma, in the range 322–932 J. The HT sputtering is energy–controlled by a pulsed injection of a neon–helium gas mixture. High–energy Ne+ and He+ ions extend the length of pulsed GIMS discharge due to the self–sputtering effect observed during the deposition of DLC and C–SiC films. These conditions result in an almost 5–fold increase in the film growth rate (up to 185 nm/min) with respect to the operation with a cold target, which is due to the assisting vapour sublimation from custom–designed graphite–based targets. The temperature boosted HT GIMS discharge, proves to be an efficient tool for reaching relatively high (∼35 %) sp3–hybridized C content in both carbon–based materials. It also allows for tailoring the energy bandgap of DLC–based optical structure, in the range from 1.7 to 2.75 eV, due to the formation of the (CC) and (CO) bonds. Higher content of silicon oxide (SiO2-x) and silicon carbide (SiC) phases (15 – 23 %) in the case of C–SiC films results in hardness increase from 21.8 to 30.1 GPa.

SiOx@Si-graphite microspheres for high-stable anode of lithium-ion batteries

The practical application of silicon (Si) anode with high theoretical capacity has not yet satisfied the commercial requirements of lithium-ion batteries (LIBs) due to serious degradation electrochemical properties arising from large volume expansion and deteriorated electrode architecture during cycling. Co-utilization of Si and graphite has become a commercially feasible method for realizing high-energy LIBs. Herein, we have synthesized a nitrogen-doped Si-graphite composite microspheres enhanced by three-dimensional carbon network by spray drying method. The three-dimensional network carbon structure generated by sodium alginate carbonization can further enhance the structural stability of the material and be favorable to the rapid transfer of electrons. The Si particle surface is partial converted into silicon oxide (SiOx) phase during sodium alginate carbonation process, which is beneficial to restrain the volume expansion effect of Si and enhance the electrochemical performance of the material. The fabricated SiOx@Si-graphite composite microspheres enhanced by three-dimensional carbon network is prospective for practical application in high-performance LIBs.

MODELING CALCULATION OF THE CORROSION RATE OF LOW CARBON STEEL IN HEAT AND POWER SYSTEMS

This article is about electrochemical analysis system of passive films corrosion properties of the thermal power equipment heating surfaces. It was found that forecasting the low carbon steel corrosion rate in thermal power systems is possible based on the multiple regression equations, which includes the amount of silicon oxide and iron hydroxide phases in the films, the fraction of free area and the active component of impedance of the films in the alkaline electrolyte and mercury. Construction of the regression equation should be carried out with the preliminary classification of data on the quantities of the active component of the film impedance of mercury and an alkaline electrolyte.

Early silicification of the Cyrenaican chert, Libya: The importance of moganite as a transitional silicon dioxide phase

AbstractThe Messinian lagoonal carbonate–evaporite sequence of Cyrenaica, north‐east Libya, hosts: (i) opaline nodules in gypsiferous microbial‐rich mudstone; (ii) nodules replacing poikilotopic gypsum cementing bioclastic carbonates; and (iii) bedded porcelanite with large lenticular gypsum pseudomorphs intercalated with recrystallized microbial mats. Optical microscopy, scanning electron microscopy, backscattered electron images – secondary electron images, X‐ray fluorescence, X‐ray diffraction and cathodoluminescence techniques were employed to elucidate on the early stages of chert diagenesis and demonstrate the role of moganite in the formation of varieties of chalcedony during silicification. The opaline nodules composed of opal‐A, exhibit shrinkage cracks lined by isopachous fibrous quartzine underlain by a thin birefringent zone. This suggests that quartzine may develop by crystallization and conversion of opal‐A through a transitional moganite. The quartzine is followed by amorphous silica gel that converts into length‐fast chalcedony. By contrast, lutecite evolved by silica replacement of gypsum through a transitional moganite phase, which forms an amorphous zone in apparent optical continuity with the fibrous lutecite; as moganite advances by pseudo‐crystalline terminations controlled by the gypsum cleavage. In gypsified oyster shells, intercrystalline organic matter enveloping pseudomorphed shell microstructures enabled moganite nucleation that merges syntaxially around the gypsum crystal rim. The associated lutecite occurs as radial‐fibrous beekite aggregates that are consistent with early shell silicification. The bedded porcelanite consists of opal‐CT groundmass undergoing recrystallization and enclosing micro‐cavities lined by quartzine. The associated pseudomorphs display phases of gypsum replacement by moganite and lutecite at the outer margin, followed by dissolution and cavity filling by quartz varieties in response to fluid flushing. In all cases, organic matter and microbes played a vital role in the silicification process.

Electrical and optical characterizations of erbium doped MPS/PANI heterojunctions

Macroporous silicon (MPS) films were yielded by electrochemical anodization of p-type crystalline silicon in HF:DMF. Following, a Schottky structure was obtained by depositing polyaniline (PANI), which was doped with different contents of erbium (Er) using cyclic voltammetry method. The structural analysis showed the formation of pores with diameters ranging between 0.25 and 1.20 μm and length around 15 μm and, after PANI deposition, the diameter became about 17% lower. The chemical characterization by Energy dispersive X-ray spectroscopy (EDS) and Rutherford Backscattering Spectroscopy (RBS) pointed out that the erbium is primarily incorporated at polyaniline surface, but it spreads through the polymer layer and achieves the MPS/PANI interface. According to the Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis, the presence of Er gave rise to the formation of additional functional groups besides that corresponding to polyaniline and silicon oxide phases. The optical characterization within the UV–vis region revealed a modified optical bandgap of PANI as a function of the Er doping concentration. The results of the electrical measurements pointed out to a lowering of the space charge region width in the silicon as well as a change of the PANI workfunction as a function of the Er doping. On the other hand, the current flow through the MPS/PANI Schottky junction was lowered by the increase of the Er doping and by the tunneling mechanism through a thin silicon oxide (≈1–2 nm) grown on MPS during PANI deposition in aqueous solution.

Estimation of the Range of Variation in the Mineral Composition of Silicate Lake Bottom Sediments Using Data from XRD and XRF

A method is proposed for estimating the range of mineral group content in the cores of silicate bottom sediments of lakes based on the search for the minimum and maximum content of stoichiometric minals that make up the group of minerals, provided that the balance of the mineral composition and the content of elements in the sample is observed. The mineral components were determined using the method of qualitative X-ray phase analysis, the contents of the main rock-forming elements were determined by X-ray fluorescence analysis. Comparison with the results of quantitative X-ray phase analysis showed that the contents of mineral groups either lie in the range calculated in the extreme search procedure based on data on the element composition, or overlap with the calculated range within the measurement error. The systematic discrepancy between the results of calculating the range of content of the silicon dioxide phase and the results of quantitative X-ray phase determination of quartz observed for the samples under consideration is due to the presence of an X-ray amorphous phase of biogenic silica. The proposed method for estimating the range of mineral group content is easy to implement, uses the publicly available MS Excel software, and can be useful for estimating variations in mineral composition by core depth, in conditions of frequent shortages of individual sample material distributed between different methods of analysis

Control of temperature changes in daily life with thermochromic green pigments

In this study, intelligent thermochromic building coatings were prepared to reduce the heating and cooling load of the building by creating a thermally comfortable building environment. Reversible effects of thermochromic building coatings between energy absorber, energy reflective states were investigated. Methyltrimethoxysilane (MTEOS), tetraethoxysilane (TEOS), thermochromic pigment-based thermochromic coatings were prepared with the sol–gel spraying method. Coatings were heat-treated at 80 °C and characterization studies were performed. It has been determined that the sample contains the silicon oxide and amorphous phase. The average grain size of the sol was found to be 6.021 μm. The development of thermochromic coatings to be utilized in buildings, urban structures were aimed. Coatings obtained in a low-cost manner exhibited thermochromic properties. The resulting coatings provided good temperature sensitivity, reversibility.

A Study of the effect of adding antimony oxide to the coating surfaces of steel and cast Iron by glass

The study included adding antimony oxide to mixtures of coating metal surfaces (Enameling), after it was selected ceramic materials used in the coating metal pieces of the type of steel and cast iron in two layers. The first is called a ground coat and the second is a cover coat.Ceramic materials layer for ground coat have been melted down inplatinum crucible at a temperature of 1200oC to prepare the glassmixture (Frit). It was coated on metals at a temperature of 780oC fortwo minutes, while the second layer was prepared glass mixture(Frit) at a temperature of 1200oC, but was coated at a temperature of760oC for two minutes.Underwent tests crystalline state of powders (Frits) and enameled samples using X-ray diffraction technique and found that the process of powders and ground coat layer is random, while the cover layer included having developed a silicon oxide and titanium oxide phases. It was measured density, coating thickness and Knoop hardness for each layer. As well as practical tests conducted dipping enameled samples in diluted and concentrated sulfuric acid, as well as diluted and concentrated hydrochloric acid for three days at a temperature of 100oC. The samples showed good resistance against these acids. The addition of antimony oxide reduced the presence of bubbles in the coated cast iron and enhancement physical and mechanical properties.

Modeling Calculation of the Corrosion Rate of Low Carbon Steel in Heat and Power Systems

This article is about electrochemical analysis system of passive films corrosion properties of the thermal power equipment heating surfaces. It was found that forecasting the low carbon steel corrosion rate in thermal power systems is possible based on the multiple regression equations, which includes the amount of silicon oxide and iron hydroxide phases in the films, the fraction of free area and the active component of impedance of the films in the alkaline electrolyte and mercury. Construction of the regression equation should be carried out with the preliminary classification of data on the quantities of the active component of the film impedance of mercury and an alkaline electrolyte.

Precisely Localizing Wavelength Sensitive Point-Spread Functions Engineered With a Silicon Oxide Phase Plate

Precisely Localizing Wavelength Sensitive Point-Spread Functions Engineered With a Silicon Oxide Phase Plate

Enhanced transmittance of sapphire by silicon oxynitride thin films annealed at high temperatures

Silicon oxynitride (SiON) and SiO2 thin films attracted considerable attention for various applications such as anti-reflection coatings and surface passivation layers. In this report, we present the enhancement of sapphire optical transmittance by over-layer deposition of the amorphous SiON by RF magnetron sputtering, and investigation on changes in microstructure and transmittance upon high-temperature annealing ∼1373 K. A thin layer of nanocrystalline SiO2 was formed at the sapphire/film interface induced by the annealing. Remarkably, the XPS spectra revealed that the silicon-nitrogen bonds disappear in the annealed films to form a non-stoichiometric silicon oxide (SiOx) phase. The films showed high visible transmittance ∼92%, which is comparable to that of soda-lime glass due to a significant reduction in the refractive index 1.41 of the films after annealing at 1373 K.

Investigation of carbon-coated silicon oxide phase changes during charge/discharge by oxygen and lithium K-Edge X-ray absorption fine structure spectroscopy

To understand the phase changes associated with the charge/discharge mechanism during cycling, we evaluated the electronic states of oxygen and lithium atoms in the high-capacity anode material SiO-C using O and Li K-edge X-ray absorption fine structure (XAFS) spectroscopy. Multiple peaks observed in the O K-edge spectrum in the 532–548 eV range were likely related to OSi bonds. During the initial charge, when SiO-C occludes Li, a new peak related to LiO bonds appeared at 534 eV. During the initial discharge, this peak was maintained at potentials below 0.7 V vs. Li/Li+, but decreased at higher potentials, suggesting the presence of a phase change point near 0.7 V vs. Li/Li+. This change was also supported by the Li K-edge spectrum. An examination of the phase change after charge/discharge cycling at negative electrode termination potentials of 0.66 and 1.1 V vs. Li/Li+ confirmed that the phase structure was stable when cycling at potentials below the phase change point, but unstable at higher potentials. Thus, stable charge/discharge cycling can be achieved by designing batteries with negative electrode termination potentials that are lower than the potential at which the phase change occurs.

Structural and optoelectronic properties of p-type SiO:H films deposited in transition zone

P-type hydrogenated silicon oxide (p-SiOx:H) films are prepared by radio frequency plasma enhanced chemical deposition with various CO2 flow rates. We use gas mixtures of carbon dioxide (CO2), hydrogen (H2), silane (SiH4) and diborane (B2H6) as reaction source gases. For all experiments the substrate temperature, pressure and power density are fixed at 200 oC, 200 Pa and 200 mW/cm2, respectively. The films are deposited on Corning Eagle 2000 glass substrates for optoelectronic measurements and on crystalline Si wafers for Fourier transform infrared (FTIR) measurement. The structural, optical and electronic properties of the films are systematically studied as a function of CO2 flow rate. The CO2 flow rate is varied from 0 to 1.2 cm3 min-1, with all other parameters kept constant. It is shown that with the CO2 flow rate increasing from 0 to 1.2 cm3 min-1, the Raman peak shifts from 520 cm-1 to 480 cm-1 and corresponding crystalline volume fraction decreases from 70% to 0. In addition, the FTIR spectrum shows that the oxygen content increases from 0 to 17% and the hydrogen bond configuration gradually shifts from mono-hydrogen (Si-H) to di-hydrogen (Si-H2) and (Si-H2)n complexes in the film. What is more, with the incorporation of oxygen, the optical band gap of each of all p-type SiO:H films increases from 1.8 eV to 2.13 eV, while the dark conductivity decreases from 3 S/cm (nc-Si:H phase) to 8.310-6 S/cm (a-SiOx:H phase). Furthermore, the oxygen incorporation tends to disrupt the growth of silicon nanocrystals due to the created dangling bonds that arises from an increased structural disorder. This leads to microstructural evolution of SiO:H film from a single nanocrystalline phase into first a mixed amorphous-nanocrystalline and subsequently into an amorphous phase. At a certain threshold of CO2 flow rate, a transition from nanocrystalline to amorphous growth takes place. The transition from nanocrystalline to amorphous silicon is confirmed by Raman and FTIR spectra. In the transition region or crystalline volume fraction of about 45%, Raman spectrum also reveals that the a mixture of nanocrystalline silicon and amorphous silicon oxide (a-SiOx:H) phase exists in the film. This means that nanocrystalline silicon oxide (nc-SiO:H) is a two-phase structural material consisting of a dispersion of silicon nanocrystals (nc-Si) embedded in the amorphous SiOx network. As is well known, the oxygen-rich amorphous phase can help enhance the optical band gap, while the nc-Si phase contributes to high conductivity. Finally, it is the SiO:H film deposited at phase transition that can realize a relatively high dark conductivity (about S/cm) with a wide optical band gap of 2.01 eV in the film. By using the transition p-layer as the window layer in conjunction with a suitable buffer thickness, we obtain a thin film solar cell with an open-circuit voltage of 890 mV, a short-circuit current density of 12.77 mAcm-2, fill factor of 0.73, and efficiency of 8.27% without using any back reflector.

Features of the mechanical treatment of rice husk for the performance of the solid-phase reaction of silicon dioxide with polyphenols

The distinguishing features of rice husk are high strength properties, chemical stability, high ash content, and low nutritional value, which are determined by the composition and structure of this type of raw material. The goal of the study was to determine optimal methods of mechanical treatment for the performance of a solid-phase reaction of silicon dioxide from rice husk with polyphenol compounds. Different regimes of the treatment of plant raw material have been compared. It has been shown that, for the solid-phase reaction of silicon dioxide from plant raw material with polyphenol compounds to occur, both the destruction of the supramolecular complex of silicon dioxide with the lignocellulose matrix, which is accomplished by fine grinding, and the plastic deformation of the silicon dioxide phase with the formation of reaction centers are necessary. These operations can be brought about using grinders with the attrition and shear modes of operation, including roller mills. It is preferable that silicon dioxide is in the composition of plant raw material since the reaction between silicon dioxide and polyphenols with the formation of surface complexes requires the presence of silanol groups. If silicon dioxide is derived from rice husk by conventional methods, most hydroxyl groups are eliminated, which significantly decreases the reactivity.

Self-assembly and growth mechanism of au nanoparticle chains in silica nanowires

We report the formation of a one-dimensional Au nanoparticle (NP) chain embedded in silica nanowires (NWs) and suggest a possible mechanism for the chain growth based on an alternative vapor-liquid-solid (VLS) process. The Au NP chain was self-assembled inside silica NWs, which were grown by high-temperature annealing of silicon substrates coated with a thick Au film. The Au NPs inside the NWs were observed to be formed by the sequent detachment of some Au from the top of a wick-like Au wire that extended from a Au lump, which was also the origin of the NWs. The results are attributed to the push-up growth of NWs by the continuous formation of a silicon-oxide phase at the top and/or on the side of a liquid Au lump via the VLS process.

A chemical route to fabricate Lu2Si2O7:Ce3+ micro-column structured films

Lu2Si2O7 (LPS):Ce3+ micro-column structured films have been prepared on silicon substrate by a chemical method which combines Si nanowire array wafers with dip-coating method. In the processing, the Si nanowire array wafers are obtained via a metal-assisted chemical etching route on single-crystal silicon (100) substrate at first step. The produced Si nanowire array wafers not only serve as guide–templates for the fabrication of LPS:Ce3+ films in a columnar fashion, but also provide Si sources for further reacting with lutetium sources at high temperatures to form LPS:Ce3+ micro-column structured films. XRD analysis indicates that as-prepared films are crystallized into a monoclinic Lu2Si2O7 phase along with an amorphous silicon oxide phase, and the latter phase ascribes to the oxidation of Si nanowire arrays. The as-prepared LPS:Ce3+ films exhibit a columnar-array structure and a uniform morphology according to SEM and TEM observations. The UV photoluminescence spectra illustrate the characteristic excitation and emission spectrum of Ce3+ ions in the host of LPS. X-ray induced emission spectrum reveals a similar shape with UV excited emission spectrum peaking at 378nm. Furthermore, the LPS:Ce3+ micro-column structured films present a fast decay time of about 3425ns. These experiments have demonstrated that the film technique thus developed is possible to fabricate column-like luminescent films of large scale with low cost.