SiOSi Bonds Research Articles

Vibrational Analysis of 3‐Glycidoxypropyltrimethoxysilane Polymer

SummaryIn this work 3‐glycidoxypropyltrimethoxysilane polymer with inorganic SiOSi bonds was prepared by a sol‐gel process. The structure of polymer was characterized by vibrational spectroscopy (Raman and IR). The interpretation of vibrational spectra is supported by the normal coordinate analysis based on density functional theory (DFT) calculations. A conformational and vibrational analysis of lowest energy dimer structure has been carried out by DFT calculations using Becke's three‐parameter exchange functional in combination with the Lee‐Young‐Parr correlation functional (B3‐LYP) and standard 6–311 + G(d,p) basis set.The comparison of theoretical spectra with the experimental data enabled us to extract the characteristic vibrational bands of polymer structure. The inorganic polymerization gives rise to siloxane network with SiOSi stretchings at 1030 and 1134 cm−1 suggesting the ladder‐type structure of GPTMS polymer.

In situ FTIR experimental results in the silylation of low-k films with hexamethyldisilazane dissolved in supercritical carbon dioxide

In situ Fourier Transform Infrared Spectroscopy measurements were performed using an innovative equipment to study the surface modification reaction between a functionalized porous MSQ-film and hexamethyldisilazane (HMDS) dissolved in CO2 at supercritical conditions (scCO2). scCO2 was used in the heterogeneous reaction due to enhancing properties, ideal for porous materials. Different infrared signatures, from the gas and solid phases, were observed and identified, implying gas–gas and solid–gas phase reactions. Among the different component signatures observed in the gas phase, carbonic acid was observed as a possible silylating gas phase nucleophilic component, while in the solid phase the predominant reaction mechanism proceeded by forming SiOSi bonds and Trimethylaminosilane (as gas phase product).

100 MeV silver ions induced defects and modifications in silica glass

A few silica glass samples having 1cm2 area and 0.1cm thickness were irradiated with 100MeV energy Ag7+ ions for the fluences ranging from 1×1012ions/cm2 to 5×1013ions/cm2. The optical properties and the corresponding induced defects were characterised by the techniques such as UV–Visible, Photoluminescence (PL), Fourier transform infrared (FTIR), and Electron spin resonance (ESR) spectroscopy. The UV–Visible absorption spectra show two peaks, one at 5eV and another weak peak at 5.8eV. A peak observed at 5.0eV corresponds to B2 band (oxygen deficiency in SiO2 network) and the peak at 5.8eV is due to the paramagnetic defects like E′ centre. The intensities of these peaks found to be increased with increase in ion fluence. It attributes to the increase in the concentration of E′ centres and B2 band respectively. In addition, the optical band gap energy, Urbach energy and the defects concentration have been calculated using Urbach plot. The optical band gap found to be decreased from 4.65eV to 4.39eV and the Urbach energy found to be increased from 60meV to 162meV. The defect concentration of nonbridging oxygen hole centres (NBOHC) and E′ centres are found to be increased to 1.69×1013cm−3 and 3.134×1014cm−3 respectively. In PL spectra, the peak appeared at 1.92eV and 2.7eV envisage the defects of nonbridging oxygen hole centres and B2α oxygen deficient centres respectively. ESR spectra also confirms the existence of E′ and NBOHC centres. FTIR spectra shows scissioning of SiOSi bonds and the formation of SiH and SiOH bonds, which supports to the co-existence of the defects induced by Ag7+ irradiation.

Curved surface effect and characteristic emission of silicon nanostructures

Some bonds on the curved surface (CS) of silicon nanostructures can produce localized electron states in the band gap. Calculated results show that different curvature can form the characteristic electron states for some special bonding on nanosilicon surface, which are related to a series peaks in photoluminescience (PL), such as LN, LO1 and LO2 lines in PL spectra due to SiN, Si=O and SiOSi bonds on the curved surface, respectively. In the same way, SiYb bond on the curved surface of Si nanostructures can manipulate the emission wavelength into the window of optical communication by the CS effect, which is marked as LYb line near 1550 nm in the electroluminescience (EL).

Polycarbonate bonding assisted by surface chemical modification without plasma treatment and its application for the construction of plastic-based cell arrays

In this paper, we introduce a strategy for adhering two polycarbonate (PC) substrates by embossing them under relatively mild conditions via simple surface chemical pre-coating without plasma treatment. Bonding was achieved by anchoring aminosilanes, specifically those with primary amines, onto the surface of the PC through urethane linkages between the amine functionality of the silane coupling reagent and the carbonyl group of the PC. Next, the terminal silanol groups on the surfaces of the two PC substrates were cross-linked via the formation of SiOSi bonds at a slightly lower temperature (125°C) than the glass transition temperature (Tg) of PC (145°C) and under atmospheric pressure (0.1MPa). The chemically treated PC surface was characterized by analyzing water contact angle, X-ray photoelectron spectroscopy (XPS), and fluorescence. The bond strength and reliability were investigated by performing pull strength test, static and dynamic leakage tests, and burst test. In addition, since the proposed bonding allowed physical detachment after the bonding, the assembly was used for the selective patterning of Escherichia coli (E. coli) on the PC surface, which proves the ability to use this technology to construct disposable plastic-based array platforms for cell studies and sensor construction in a highly cost-effective manner.

Optical basicity and chemical bonding of Bi2O3 containing glasses

Average single bond strength BM–O in kJ/mol of an averaged metal-oxide ion (M–O) chemical bond has been estimated for Bi2O3–P2O5, Bi2O3–B2O3, Bi2O3–SiO2, Bi2O3–GeO2, and CdO–Bi2O3–B2O3 glasses using single bond strength data for simple oxides. It has been found that a decrease in the BM–O is accompanied by an increase in the refractive index based optical basicity Λ(no) of the glasses. The glasses with high Bi2O3 contents of about ~40–70mol% possess smaller values of the average single bond strength in the ~300–160kJ/mol range than the glasses with high B2O3, P2O5, SiO2, and GeO2 contents of about ~80–90mol% (~430–300kJ/mol). It has been assumed that the decrease in the interaction parameter and average single bond strength and the increase in the optical basicity in bismuthate glasses with increasing Bi2O3 content could be connected with the formation of mixed BiOB, BiOP, BiOSi, and BiOGe along with BiOBi bonds which leads to the increased ionicity in comparison with more covalent POP, BOB, SiOSi, and GeOGe bonds. The number of mixed bonds and BiOBi bonds increases and the number of POP, BOB, SiOSi, and GeOGe bonds decreases with increasing Bi2O3 content. An equation for the calculation of optical basicity of SiO2 in Bi2O3–SiO2 glasses has been also suggested taking into account the contribution of different structural units namely SiO40, SiO4−, SiO42−, SiO43−, and SiO44− groups.

Effect of phosphate–silane pretreatment on the corrosion resistance and adhesive-bonded performance of the AZ31 magnesium alloys

A phosphate–silane surface treatment is developed to improve the corrosion resistance of phosphated magnesium AZ31 by dihydric phosphate solution. Silane KH560 solution is selected to treat the phosphated magnesium AZ31 alloys. The morphology, thickness and composition of the coating and the corrosion resistance of the coated samples are studied by scanning electron microscopy (SEM), XPS analyses and corrosion tests (including hydrogen evolution detection and EIS). An about 2μm silane coating consisting of SiOSi and SiOMg bonds is formed on the surface of the phosphated magnesium alloys. The silane coating apparently improves the corrosion resistance, adhesive bonded performance and durability in hot-humid environment of the phosphated magnesium AZ31 alloys by means of increasing the polarization resistance RpCP in NaCl solution, initial bond strength and residual bond strength of adhesive-bonded joints in hot-humid environment. The improvement of silane pretreatment on the corrosion resistance and adhesive-bonded performance of phosphated Mg AZ31 is attributed to the improvement of SiOSi bonds in silane coating on the intermolecular interaction between the adhesive and phosphate coating and sealing effect of silane coating to the micro pores in phosphate coating.

Properties and Antimicrobial Activity of Nanosilver Deposited Cotton Fabric Coated with γ-Methacryloxypropyl Trimethoxysilane

The simple and industrially adjustable process of silver nanoparticles deposition on cotton fabric followed by coating with γ-methacryloxypropyl trimethoxysilane (MPS), as well as the properties of obtained nanocomposite has been investigated. Silver nanoparticles were prepared through the reduction of silver nitrate with sodium borohydrate and deposited on cellulose fabric. In order to stabilize obtained nanostructured material and improve its properties, the fabric was treated by immersion in cross linkable MPS. The morphology of the finished fabrics was characterized by Scanning Electron Microscopy (SEM). It has been determined that process does not impair nanocharacter of silver particles and yield uniform distribution throughout the fabric surface. The concentration of Ag in the fabric samples was determined by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The average deposited amount of nanoparticles was found to be 63 ppm and 48 ppm for samples without and those with MPS, respectively. The character of obtained polysiloxane coating was examined using Fourier Transform Infrared (FTIR) spectroscopy. The presence of SiOSi bonds on the cellulose surface pointed out to self-condensation between silanol groups. Differential Thermal and Thermo-Gravimetric Analysis (DTA/TGA) revealed that MPS deposited on fabric provided modification of thermal properties. The change of the surface properties after the modification was ascertained by contact angle measurements. The antimicrobial activity of the antibacterial finish on the cotton fabric, expressed as bacterial reduction efficiency, has been determined. Bacterial reduction of at least 88.5% against both, Staphylococcus aureus and Escherichia coli, has been obtained.

Improvement of electrical properties of silicon oxide thin film with ultraviolet and organic gas assisted annealings

In order to form a silicon oxide thin film at a low temperature, we employed the reaction between spin-coated silicone oil and ozone gas at a low temperature of 250°C. In the formed silicon oxide films, a large number of SiOH bonds were observed. To reduce the amount of impurities such as SiOH bonds, the silicon oxide film underwent ultraviolet (UV) light treatment and alcohol-assisted annealing. The combination of dipping in ethanol and thermal annealing in methanol gas effectively reduced SiOH bonds. It was hypothesized that the SiOH bonds were displaced with SiOCH3 bonds due to the alcohol treatment. After UV treatment and alcohol annealing, the network SiOSi bonds increased, and the cage SiOSi bonds decreased. It was predicted that the cage SiOSi bonds were broken by UV light and the bonds recombined to form the network SiOSi bond. The dielectric property after UV treatment and alcohol annealing was improved owing to the decrease in the cage SiOSi and SiOH bonds.

Preparation and characterization of silicate nanofilms doped with europium β-diketonate complexes

Films consisting of Eu3+ β-diketonate complexes were deposited onto glassy substrates by means of the spin- and dip-coating techniques, using different ion/ligand ratios. Absorption spectroscopy in the infrared region revealed the typical stretching bands of the SiOSi and SiOH bonds of the inorganic matrix as well as bands relative to the CO and CH symmetric vibration of β-diketone (dibenzoylmethane). The films displayed UV-visible absorption band at 350nm, attributed to the organic ligand. Luminescence properties were studied by photoluminescence spectroscopy. Upon ligand excitation, the emission spectra exhibited the characteristic bands of the Eu3+ ion corresponding to the transition from the excited state 5D0 to the ground state 7FJ. Scanning electron microscopy confirmed the formation of a film with average thickness ranging from 80 to 100nm. The sol–gel process and the deposition techniques resulted in the effective formation of nanofilms, which opens up perspectives for their application in photonics.

Dynamics of fractoluminescence, electromagnetic and acoustic emissions upon impact on a granite surface

The dynamics of fractoluminescence (FL), electromagnetic (EME) and acoustic emissions (AE) induced in a granite sample by a striker blow was studied. The impact causes strong irregular vibrations in the striker-sample system. About 900 μs after the impact, the amplitude of these vibrations decreases approximately by a factor of 100. As granite possesses piezoelectric properties, the mechanical vibrations induce equally strong electromagnetic oscillations. FL arises about 60 μs after the impact. The FL spectra contain the bands of ≈1.9 and 2.6 eV, which means that under the impact, the SiOSi bonds are broken and SiO·free radicals and Si: centers are formed. FL appears as a series of flashes with a duration of ≈10 ns. Each flash is assumed to correspond to the initiation of a microcrack. The linear sizes of the microcracks estimated from the intensity of the flashes and the velocity of elastic waves range from ≈7 μm to ≈40 μm, with an average of ≈10 μm. The microcracks are grouped in microseries with a duration of ≈4μs, which causes modulation of strong AE oscillations by weak oscillations with a period of ≈8 μs. The formation of microcracks with a linear size exceeding ≈30 μm causes discontinuities in the time dependence of EME.

The role of ultraviolet radiation during ultralow k films curing: Strengthening mechanisms and sacrificial porogen removal

This work proposes a fundamental understanding of structural transformation occurring during porogen extraction from as-deposited ultralow k (ULK) materials when exposed to ultraviolet (UV) radiation during thermal curing. Specific explanations are provided for as deposited films at high temperature (T>250 °C). This temperature range is sufficient to assess thin-film stability. Two distinguished regimes were identified in the curing process. During the first stage, the film shrinks strongly in similar proportion to SiCH3 break. Preferential impact of UV radiation on hydrocarbon porogen bonds leads also to a break of SiCH3 structures. In this work, 5 min of curing is enough to remove the porogen and create the max of porosity (33%). After the porogen removal step, the porous film shrinks under UV radiation leading to an increase of SiOSi bond concentration. A structural rearrangement of the bulk is initiated since the porogen is totally evacuated from the film. The increase of normalized infrared SiOSi peak during UV curing (related in literature to an improvement of mechanical properties) is mainly due to film densification (a few SiOSi bonds creation). The origin of shrinkage is explained by the breaking of SiCH3 which could turn into a SiH bond leading to a free volume reduction within the film. In this case, a correlation is found between shrinkage and elastic modulus. The resulting SiOSi structure densification drives, at first order, the improvement of the mechanical properties. UV radiation exposure shows no effect in silanol condensation and acts mainly on the porogen decomposition and bulk densification. Si-CH2-Si structure formation, pointed out in the literature as a possible reaction way to enhance film crosslinking, is identified in the nuclear magnetic resonance (NMR) broadband spectrum of the ULK film. However, resulted NMR and infrared peaks intensities suggest its formation as a minor. This study gives a full understanding of UV curing impact on ULK films (k≤2.5) where structure densification is identified as a main process to enhance the film strength in addition to the crosslinking.

Investigation of Silicalite-1 Crystallization Using Attenuated Total Reflection/Fourier Transform Infrared Spectroscopy

The crystallization of silicalite-1 in aqueous sols has been investigated using ATR/FTIR spectroscopy as a function of sol composition. The existence of oligomeric siliceous species has been verified for all compositions after the end of tetraethoxysilane (TEOS) hydrolysis. On the other hand, more condensed and highly cross-linked siliceous structures have been observed only at the sols of high SiO2 concentrations. These structures have been considered to be the “primary” nanoparticles reported by other researchers, and their IR spectra revealed that their structures are different from that of the silicalite-1 crystals. The evolution of the nanoparticle structure as a function of crystallization time has been monitored. It has been found that, upon heating of the synthesis sols, the “primary” nanoparticles transform to a new form that has an increased number of SiOSi bonds. These “intermediate” particles do not have the structure of silicalite-1, and they are present for most of the crystallization. Finally, once the silicalite-1 nuclei are formed, they grow in a suspension of these “intermediate” particles.

Structural Transformation in PECVD Ultralow-k Material during Porogen Removal by UV Assisted Thermal Curing

ABSTRACTNext-generation microelectronic interconnects require the use of dielectrics with continuously lower permittivity (k) to overcome limitations induced by crosstalk parasitic signal delay. Using PECVD, Ultralow-k film (ULK, k ≤ 2.5) can be developed by creating pore inclusions within an organosilicate matrix through porogen approach. Both ULK deposition and subsequent curing process has to be adjusted in order to achieve optimized mechanical and electrical properties and maintain stability during integration. For this concern, the attention was recently focused on ultraviolet (UV) radiation to sustain the thermal curing. In the present work, a fundamental understanding of structural transformations occurring during porogen extraction from as-deposited ULK materials when exposed to thermal-assisted UV radiation is proposed. This thermal-assisted UV cure technique is very efficient in porogen removal since in a few minutes the desired porosity is reached. During the first stage of curing, the film shrinks strongly whereas the porosity is created. After porogen removal step, the porous film continues shrinking under UV radiation leading to an increase of SiOSi bonds concentration (film densification). The normalized FTIR SiOSi peak increase during UV curing (related in literature to an improvement of mechanical properties) is mainly due to the film densification, in addition to the SiOSi bridging bond creation. In this case, correlation is found between shrinkage and elastic modulus.

Growth of titanium silicate thin films by photo-induced chemical vapor deposition

Titanium silicate thin films have been grown on Si substrates by photo-induced chemical vapor deposition using 222-nm ultraviolet excimer lamps. Titanium tetraisopropoxide (TTIP) and tetraethoxysilane (TEOS) were used as precursors. TTIP and TEOS were dissolved together in cyclohexane and introduced into the photochemical reaction chamber through a droplet injector vaporizer. The composition of the film was controlled by changing the ratio of TTIP to TEOS in the precursor solution. High quality titanium silicate films with various Ti/Si ratios and low carbon content have been achieved as revealed by X-ray photoelectron spectroscopy measurements. The atomic percentage of Ti content in the grown silicate films is significantly larger than that in the precursor solution. The films were measured to be 30–80 nm in thickness and 1.91–2.31 in refractive index by ellipsometry. Both the growth rate and refractive index increase with increasing Ti percentage in the silicate films. The evolution of Fourier transform infrared spectra of the silicate films with solution composition shows that the TiOSi absorption at approximately 920 cm−1 becomes stronger, while the TiO absorption at approximately 430 cm−1 becomes weaker with decreasing Ti percentage in the solution. A small feature at ∼1035 cm−1 related to SiOSi bonds is also observed in the SiO2-rich Ti silicate film.

Nonhydrolytic synthesis and structural study of methoxyl-terminated polysiloxane D/Q resins

Low-viscosity, methoxylated polysiloxane resins incorporating Me 2 SiO 2/2 (D) and SiO 4/2 (Q) units were prepared using nonhydrolytic condensation between Si-Cl and Si-OMe groups with the formation of MeCl, catalyzed by a Lewis acid. With the commonly used catalysts, condensation between two Si-OMe groups, with formation of Me 2 O, also took place to a large extent, hindering the control of the degree of condensation of the resins. Several catalysts were tested by monitoring the formation of MeCl and Me 2 O using sealed NMR tubes and 1 H-NMR spectroscopy. The best compromise between reactivity and selectivity was obtained with ZrCl 4 . Resins with various compositions were prepared in the absence of solvent by condensation between Me 2 SiCl 2 and Si(OMe) 4 at 130°C, catalyzed by 1 mol % ZrCl 4 . They were characterized using viscosimetry, gas chromatography coupled with mass-spectrometry (GC-MS), and quantitative 29 Si-NMR spectroscopy. The resins consisted of a complicated mixture of oligomers, linear or branched (n > 1) and cyclic (n > 3), with a high degree of D/Q bonding. The distribution of Si-OMe and Si-OSi bonds and the bonding between D and Q units were found to be nearly random. This was ascribed to the occurrence of Si-OSi/Si-OMe and Si-OSi/Si-OSi redistribution reactions that reached equilibrium during the synthesis.

Synthesis of [(Trialkoxysilyl)propyl]imides

Imidization reactions between anhydrides and (alkoxysilyl)propylamines containing alkorysilane groups result in hydrolysis and condensation of the alkoxysilane groups and formation of SiOSi bonds. As a result, the direct reaction of various anhydrides with (γ-aminopropyl)trialkoxysi- lanes did not afford [(trialkoxysilyl)propyl]imides but instead resulted in insoluble crosslinked materials. A successful two-step synthesis of [(trialkoxysilyl)propyl]imides is reported. In the first step, an inter- mediate imide was prepared by reaction of an anhydride with 2-aminopy- ridine. Following removal of the water of imidization, addition of an (γ-aminopropyl)trialkoxysilane resulted in a transimidization equilibri- um which favored displacement of 2-aminopyridine and formation of a [(trialkoxysilyl)propyl]imide in high yield. Synthesis of a moisture- curable polyimide containing alkoxysilane endcaps is briefly described

SiSSi and SiOSi bonds in molecules and solids: A comparison

Ab initio STO-3G molecular orbital calculations completed for various silicon sulfide molecules have reproduced bridging bond length and angle variations of molecular and solid state thiosilicates. Calculated potential energy curves for SiSSi and SiOSi bonds conform with the narrow range of angles (106°–115°) observed for thiosilicates and the wide range (120°–180°) observed for silicates. In addition, the limited range of angles of the SiSSi bond agrees with the limited range of topologies and configurations exhibited by molecular and solid thiosilicates as compared to the wider range of angles, topologies and configurations exhibited by siloxanes and silicates. Quadratic stretching and bending force constants calculated for the silicon sulfide molecules agree with experimental values. The close correspondence of bond length and angle variations in molecular and solid thiosilicate systems indicates that the local bonding forces in both systems are practically the same notwithstanding the long range forces of the solid.

Investigation of the synthesis and hydrolytic degradation of polyborodimethylsiloxanes

The interaction of polydimethylsiloxanediols with boric acid has been investigated at 180–200° by infrared spectroscopy. The existence of intermolecular coordination interaction has been deduced from changes in the intensities of absorption bands relating to SiOH, SiOSi, BOSi, BOS and BOH bonds. The hydrolysis of polyborodimethylsiloxanes under various conditions has been investigated by PMR and IR spectroscopy. In the light of the results obtained some conclusions have been drawn regarding the mechanism of polyborodimethylsiloxanes formation, and regarding their microstructure.