Silicon-oxygen Compounds Research Articles

Modelling atomic and nanoscale structure in the silicon–oxygen system through active machine learning

Silicon–oxygen compounds are among the most important ones in the natural sciences, occurring as building blocks in minerals and being used in semiconductors and catalysis. Beyond the well-known silicon dioxide, there are phases with different stoichiometric composition and nanostructured composites. One of the key challenges in understanding the Si–O system is therefore to accurately account for its nanoscale heterogeneity beyond the length scale of individual atoms. Here we show that a unified computational description of the full Si–O system is indeed possible, based on atomistic machine learning coupled to an active-learning workflow. We showcase applications to very-high-pressure silica, to surfaces and aerogels, and to the structure of amorphous silicon monoxide. In a wider context, our work illustrates how structural complexity in functional materials beyond the atomic and few-nanometre length scales can be captured with active machine learning.

Silicon Oxides as a Competitive Material for Photoanodes

A water photosplitting process is an approach to electrochemical direct solar energy conversion into electricity, hydrogen fuel and chemical energy which is stored in the form of oxygen. A water photosplitting process requires oxidatively robust and inexpensive photoanodes. Nowadays the most often considered and studied material is titanium dioxide (TiO2), but the competitive material for such a photoanode which is the silicon oxides, should be seriously considered because of their much more suitable bandgap (Eg) for sun light absorbtion (between 1,6 eV and 2,4 eV comparing to 3.2 eV for TiO2) and their chemical stability in water solution.. Furthermore, a wide prevalence of silicon in the lithosphere, a source of its oxides, has to be bear in mind.In the seventies and eighties it was proved that different bulk silicon oxide types (SiOx) exist [1, 2]. These compounds are semiconductive and their electronic energy band gap is between 1.12 eV, for the bulk silicon, and 8.9 eV, for the bulk silica [3] Furthermore, it was shown that silicon oxide, SiO, might increase photoeffect of a mono crystalline silicon electrode and might protect such an electrode against corrosion in water solution [4, 5]. The aim is to find electrochemical conditions with the use of reagents usually available on the market, which would lead to the production of the photoactive material based on the silicon and silicon oxides, SiOx [5-7].In this presentation the formation of SiOx films by electrodeposition [8] and its electronic surface characterization will be discussed. It will be pointed that photoelectrochemical water oxidation at the electrochemically obtained SiOx films can be observed at the onset potentials lower than 0.2 V vs. NHE. Comparing this value to the dark water splitting potential, (1.23 V) means energy saving corresponding to ca. 1 V. The photoactivity of SiOx photoanodes was highly reproducible and the observed photocurrent sustained for many hours. The electronic properties of the electrodeposited films will be discussed on the base of UV-Vis and XPS data. The main point of the discussion will be put on the determination of Eg for the multicomponents semiconductive films. The advantages and disadvantages of both techniques will be discussed. It will be shown that electrosynthesized films consist of Si, SiO and Si2O3. Additionally, the influence of morphology determined by AFM and SEM microscopy on photoactivity of the semiconductive films will be discussed as well. G. Dearnaley, D. V. Morgan, A. M. Stoneham, A model for filament growth and Switching in amorphous oxide films, J. Non-Cryst. Solids 4 (1970) 593E. B. Priestley, P. J. Call, Deposition and characterization of thin SiOx films, Thin Solid Films 69 (1980) 39Z. A. Weinberg, G. W. Rubloff, The Physics of SiO2 and its interfaces, Pergamon, New York, 1978, p. 24 (SiO2), p. 136 (Si)R. Corriu, P. Jutzi, Taylor-Made Silicon-Oxygen Compounds, from Molecules to Materials, Vieweg. Wiesbaden, Germany, 1996M. Szklarczyk, J. O’M. Bockris, Photoelectrocatalysis and Electrocatalysis on p- Silicon, J. Phys. Chem. 88 (1984) 1808M. Szklarczyk, J. O’M. Bockris, V. Brusic, G. Sparrow, Substrate Effects on Photoelectrochemical Kinetics, Int. J. Hydrogen Energy9 (1984) 707M. Szklarczyk, R. A. Allen, Interpretation of quantum yields exceeding unity in photoelectrochemical systems, Appl. Phys. Lett. 49(1986) 1028A. Krywko-Cendrowska, M. Strawski, M. Szklarczyk, Low temperature electrodeposition of SiOx films photoactive in water solution, Electrochimica Acta, 108 (2013)112

Features of chemical and mineral composition of a rammed compensation layer of a lining after service

Results are provided for a study of a rammed compensation layer of the lining of a ferroalloy furnace RTP-2 after service. It is established within the layer gaseous components from oxygen compounds of silicon, titanium, aluminum, iron, and also gaseous potassium and titanium, condense in the layer and are disproportionated. In the carbon mass there is precipitation of silicon monoxide, and reaction products of both complexes and rammed layer carbon material.

A mechanism of oxygen-induced passivation of porous silicon in the HF: HCl: C2H5OH solutions

The problem of stabilizing the properties of porous silicon films was studied. A thermodynamical analysis of electrochemical processes occurring in the course of anodic Si dissolution is performed. A new description of electrode reaction of silicon interaction with hydrofluoric acid is suggested. It is shown that hydrogen-induced passivation of the Si surface governs the equilibrium dissolution potential of the silicon electrode. Thermodynamic calculations indicate that it is possible to substitute the chemically and thermally unstable surface groups (of the SiHx type) for more stable silicon-oxygen compounds directly in the course of formation of porous Si in electrolytes with the addition of strong hydrohalic acids. The results obtained made it possible to explain thermodynamically the stabilizing effect of an HCl additive in electrolytes used for formation of porous Si on its chemical and physical properties.

A density-functional-based tight-binding scheme for the study of silicon- oxygen compounds

Crystalline and molecular silicon-oxygen compounds are investigated using asimplified LCAO-LDA scheme for the construction of a nonorthogonal tight-binding Hamiltonian within a two-centre approximation. The repulsive part ofthe potential is derived as a universal short-range pair potential fromfitting the difference between the band structure energy of proper molecularsystems and the corresponding SCF-LDA cohesive energy curves. The methodallows, under consideration of the electronic states, molecular dynamicssimulations of large finite as well as condensed systems. The applicabilityof this method to the important class of silicon oxides and related moleculesis demonstrated. In particular, the properties of the equilibrium structureof α-quartz and several siloxane molecules are calculated and are foundto agree well with both experiment and self-consistent calculations. To obtainsuch a good agreement, it is necessary to also include the unoccupied 3dstates of Si into the LCAO basis of the wave functions.

Investigation of Crystalline Quartz and Molecular Silicon-Oxygen Compounds with a Simplified LCAO-LDA Method

AbstractCrystalline and molecular silicon-oxygen compounds are investigated using a simplified LCAO-LDA scheme for the construction of a nonorthogonal tight-binding (TB) Hamiltonian within a two-center approximation. The applicability of this method to the important class of silicon oxides and related molecules is demonstrated. In particular, the properties of the equilibrium structure of α-quartz and several Siloxane molecules are calculated and found to agree well with experiments and self-consistent calculations. To obtain such a good agreement it is necessary to include also the 3d states of Si into the LCAO basis of the wavefunctions.

Visible Photoluminescence From Rapid-Thermal-Oxidized Porous Silicon

AbstractWe have studied the origin of the visible photoluminescence (PL) from oxidized porous Si. The hydrogen–passivated surface of porous Si prepared by electrochemical etching is converted to stable silicon oxides by rapid–thermal–oxidization processes. At low oxidation temperature (Tox), the PL spectrum with a peak near 700 nm is observed. At high Tox above 800 °C, a strong blue PL is observed near 400 nm. We discuss the origin of blue and red PL by employing the results of ab initio electronic structure calculations of silicon–oxygen compounds.

Systematic survey of cyclic silicon-oxygen compounds

Compounds with 0, 1, 2, or 3 oxygen atoms bridging 2 silicon atoms are investigated by ab initio calculations. Two such series of compounds, with and without a formal central Si-Si bond, are considered. The triplet states of the former set are also examined. For some of these compounds, the present calculations represent the first time they have been examined at a sufficiently rigorous level of theory. For the compounds that are formally bonded, this level is two configuration SCF (TCSCF) for singlets and ROHF for triplet states, using split valence polarized basis sets. The main result is that no central Si-Si bond exists when there are 2 or 3 bridging oxygens; instead, these are biradical species.

Charge calculations in molecular mechanics. Part 8 Partial atomic charges from classical calculations

The CHARGE2 programme, which involves the classical calculation of both the inductive and resonance contributions to the partial atomic charges in molecules is described, and the charges and electrostatic potentials obtained presented for some illustrative examples. In substituted methanes (CH3X, CF3X, CCl3X) the effects of varying the electronegativity of the substituents and the alpha- and beta-substituent contributions are clearly illustrated for a variety of substituent groups X. The problems involved in the inclusion of silicon into this scheme are detailed, together with the methods of overcoming them. The partial atomic charges (sigma and pi contributions) and electrostatic potentials for some silicon oxygen compounds are presented and discussed. The partial atomic charges from CHARGE2 for all the natural amino acids as their N-acetyl, N'-methylamides are given and compared with those obtained from the AMBER and ECEPP/2 force fields. Considerable differences in these figures are observed, with the AMBER charges consistently much larger than those from the other two methods. The CHARGE2 partial atomic charges and electrostatic potentials for the four common nucleic acids, adenine, cytosine, guanine and thymine, are given and compared with those derived from other calculations. Again there is general similarity but also there are considerable differences, with those from the AMBER force field somewhat larger than the other methods.

Electronic structure of the 3.SIGMA.- states of silicon-oxygen compounds, SiOSi and SiSiO

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure of the 3.SIGMA.- states of silicon-oxygen compounds, SiOSi and SiSiORoger L. DeKock, Brian F. Yates, and Henry F. Schaefer IIICite this: Inorg. Chem. 1989, 28, 9, 1680–1684Publication Date (Print):May 1, 1989Publication History Published online1 May 2002Published inissue 1 May 1989https://doi.org/10.1021/ic00308a017RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (634 KB) Get e-Alerts Get e-Alerts

Auger and photoelectron line energy relationships in aluminium-oxygen and silicon-oxygen compounds: C D Wagner et al, J Vac Sci Technol, 21 (4), 1982, 933–944

Auger and photoelectron line energy relationships in aluminium-oxygen and silicon-oxygen compounds: C D Wagner et al, J Vac Sci Technol, 21 (4), 1982, 933–944

Auger and photoelectron line energy relationships in aluminum–oxygen and silicon–oxygen compounds

Silicon–oxygen and aluminum–oxygen compounds exhibit significant XPS Auger and photoelectron chemical shifts that are accurately measurable. Chemical state plots of KLL Auger kinetic energy versus 2p photoelectron energy permit identification of chemical species from the locations of their points on the plots. The KLL Auger electrons of Al and Si were generated by the bremsstrahlung component of the radiation, with conventional instrumentation. The location of points on the plots can be understood on the basis of polarizability of the environment (on the Auger parameter grid of lines, slope +1) and on the basis of the factors contributing to the energy of the final state ion in the Auger transition (a grid of line, slope −1). Tetrahedral aluminum has a significantly smaller Auger parameter than octahedral aluminum, and this difference is repeated, but with reduced magnitude on the similar plots for silicon and oxygen lines for the same compounds. Otherwise, the Auger parameters for this class of compounds are remarkably uniform. The Auger parameter values for oxygen and sodium in these compounds, using the 1s and KLL lines, are relatively small compared to those of other compounds of oxygen and sodium. For compounds of similar Auger parameter, differences in Auger final state ion energy are interpretable on the basis of electron density on aluminum and silicon atoms in the initial state, due to extent of bonding to oxygen, or to amount of negative formal charge on the silicate structure. Inclusion of tetrahedral aluminum enhances the negative charge and decreases the final state ion energy in high alumina zeolites. The difference between the energies of the O1s and Si2p lines in the inorganic silicon compounds is almost invariant, 429.0 to 429.6 eV. The three silicon polymers examined have a significantly larger line difference, 429.8 to 430.1 eV, making possible a differentiation between silicones and silicates. The oxygen KVV lines, with Auger transition final vacancies in valence levels, have shapes characteristic of chemical structure. The uncharged Si–O–Si structure exhibits a well-defined shoulder; in Al–O–Si the shoulder is so close in energy it merely gives rise to asymmetry in the peak; Al–O–Al and charged Si–O–Si give oxygen KVV lines as single sharp peaks.

Chemical State Analysis of Silicon-Oxygen Compounds

Chemical states of so-called silicon monoxide, powder and evaporated films, were studied by fluorescent X-ray spectroscopy(FXS), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy(AES). Si Kα and Kβ spectra show the existence of small amounts of SiOx(0<x<2) in addition to the main Si-SiO2 structure. Although in the AES measurement, SiOx could not be found, the XPS results showed the clear evidence of SiOx. The silicon monoxide has, based on these measurements, Si and SiO2 mainly and small amounts of SiOx.

X-ray photoelectron study of some silicon-oxygen compounds

Abstract More than fifty specimens of silicon-oxygen compounds have been studied by X-ray photoelectron spectroscopy. Due to the insulating properties of these specimens the measured binding energies of the various atomic levels were corrected using the C (1 s ) line due to hydrocarbon contamination as a reference. A statistical treatment of the experimental results has been used to verify the validity of the reference and to discuss the differences in binding energy of the Si (2 p ) line in various samples. Three different steps of oxidation have been found for silicon; the chemical shifts with respect to unoxidised silicon are 3.2, 4.1 and 5.0 eV for surface oxidised silicon, silicates and quartz, respectively. The influence of atoms other than oxygen in the neighbourhood of silicon, such as fluorine or alkaline cations is discussed.

Force constants and bond lengths in oxygen compounds of silicon, germanium, and phosphorus

Force constants and bond lengths in oxygen compounds of silicon, germanium, and phosphorus

Polymorphism of molecules and complex ions in oxygen compounds of silicon and phosphorus Communication 5. Phase transitions and structure of molecules of cyclic dimethylpolysiloxanes

1. A spectroscopic investigation of cyclic dimethylpolysiloxanes indicates great deformability of the rings, all the way up to a change in the conformation, at changes from −100° and above. 2. Transition from the crystalline phase to the liquid phase, in the case of rings with an even number of siloxane “bridges” Si-O-Si, leads to a change in the conformation of the closed chain from a configuration with “identity period” of two units (trans-) to a configuration in which the “identity period” is formed by one unit (cis-). 3. Dimethylpolysiloxanes with an odd number of siloxane units in the ring possess the same conformation in the liquid and crystal, analogous to the conformation of the rings with an odd number of units, characteristic of the liquid phase.

Polymorphism of molecules and complex ions in oxygen compounds of silicon and phosphorus. Communication 4. Phase transitions and conformations of the octamethylcyclotetrasiloxane molecule [OSi(CH3)2

1. The phase transition in crystalline octamethylcyclotetrasiloxane is due to transition of the molecules from Ci to S4 symmetry. During melting, a further change in the structure of the molecule occurs; in the liquid phase it apparently possesses C4 symmetry, which is also preserved in the gas phase. 2. The transformations of the molecule [OSi(CH3)2]4 consist of a change in the conformation of ring and do not lead to any significant change in the bond lengths and valence angles in the ring. A vital role in the mechanism of the molecular rearrangement is played by the lability of the SiOSi angle-thermal excitation of the nonplanar deformational vibrations of the siloxane ring.

Polymorphism of molecules and complex ions in oxygen compounds of silicon and phosphorus

1. An investigation of the thermal variations of the IR spectrum of ZrP2O7 permits us to relate the phase transition at 300° to inversion of the P2O7 anions and indicates the existence of several minima of the potential function of the vibration δPOP, symmetrical with respect to the configuration with ∠POP = 180°. 2. The IR spectra of Mn2P2O7, Sc2Si2O7, and Er2Si2O7 give evidence of a centrally symmetrical form of the anion X2O7 and do not exhibit transition to the bent configuration all the way down to −150°. 3. The possibility of a change in form of the potential function of the vibration δXOX in X2O7 ions is assumed within broad limits: from centrally symmetrical but, possibly, highly anharmonic (or even with a small central maximum) to a configuration with a barrier around 0.1–0.01 eV at < XOX = 180°, and to a curve with one minimum at XOX ≠ 180° (the “usual” bent ions X2O7). 4. Redistribution of the dπ — pπ bonds in the anion X2O7 with increasing fraction of covalent character in its interaction with the cations leads to an increase in the equilibrium value of < XOX and promotes inversion of the anion.

Polymorphism of molecules and complex ions in oxygen compounds of silicon and phosphorus. Report 2. On the mechanism of the phase transition in Mg2P2O7

1. The IR spectrum of Mg2P2O7 crystals was investigated and interpreted in the temperature range from −150 to 150°. In the low-temperature form of Mg2P2O7, the intrinsic symmetry of the P2O7 ions does not exceed Cs or C2 at a value of the angle POP no greater than 150–160°. The spectrum of the high-temperature modification of Mg2P2O7 formally satisfies the selection rules for a centrally symmetrical configuration of the anion (< POP=180°). 2. A consideration of the characteristics of the spectrum of the high-temperature modification and the changes in the bands of the internal vibrations of the P2O7 anion with changing temperature leads to the conclusion of a statistical character of the central symmetry of the anion. It is assumed that the potential function of the vibration δPOP possesses two minima, while the mechanism of the phase transition in Mg2P2O7 is related to thermal excitation of inversion of the anion.

Polymorphism of molecules and complex ions in oxygen compounds of silicon and phosphorus. Report 1. Nature of the Si-O-Si bonds and values of the valence angles of oxygen

1. Changes in the order of the bonds R3'Si-OR as a function of the nature of the substituents R and R′ have been discussed on the basis of the literature data and original data. 2. The high sensitivity of the valence angle of the “bridge” oxygen atom in X-O-X bonds (X=Si, P) to variation of the nature of these bonds, primarily determined by the participation of dπ-pπ bonds, has been demonstrated.