Si-N Bonds Research Articles

Molecular dynamics study of the effect of composition on elastic properties of silicon oxynitride films

Abstract Understanding mechanical properties of silicon oxynitride (a-SiON), a key insulating material, is vital for electronic device design and reliability. Though the effects of fabrication conditions on a-SiON have been studied, the underlying relationship between its atomic-scale structure and mechanical properties remains unclear. This study investigates the relationship between elasticity and atomic-scale structures in a-SiON by molecular dynamics simulations with a universal graph neural network interatomic potential. The bulk modulus increases from 49 to 140 GPa with higher N content. N atoms form N2 molecules under O-rich conditions, hindering bulk modulus increase, and form an Si3N4-like network under O-poor conditions, enhancing bulk modulus. Formation energy calculations indicate N2 formation is preferable under O-rich conditions. Meanwhile, under O-poor conditions, Si-N bond formation is preferable, which reinforces a-SiON by increasing bond density. The findings suggest realizing O-poor conditions is crucial for highly elastic insulating films.

Role of ex-situ HfO2 passivation to improve device performance and suppress X-ray-induced degradation characteristics of in-situ Si3N4/AlN/GaN MIS-HEMTs

The role of ex-situ HfO2 passivation in in-situ Si3N4/AlN/GaN-based metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) to improve the device performance and protect the device from severe degradation under high-energy X-ray irradiation has been investigated. Here, the root cause and mechanism for the degradation have been studied utilizing different material/device characterizations. X-ray photoelectron spectroscopy results suggest that several Si-N bonds in stoichiometric Si3N4 and Hf-O bonds in HfO2 passivation film can be broken under X-ray irradiation, where numerous charges might be trapped easily and deteriorate the interface quality. Furthermore, due to the generation of chemical vacancies under X-ray, a band tail near the edge of valence band maximum in Si3N4 and HfO2 films can be created. The obtained results suggest that MIS-HEMT fabricated with an atomic layer deposited (ALD)-HfO2 (MIS-HEMT B) has relatively greater performance compared to MIS-HEMT fabricated without ex-situ HfO2 (MIS-HEMT A) according to the higher maximum drain current (Idmax), peak transconductance (gmmax) and lower current collapse, denoting the effectiveness of ALD-HfO2 to passivate the surface traps. It is noticed that X-ray irradiation induces numerous negative charges in the dielectric layers and degrades the device performance. Interestingly, after X-ray irradiation, the degradation rates in Idmax, gmmax, and current collapse are significantly lower in MIS-HEMT B compared to MIS-HEMT A, suggesting the potential irradiation hardening mechanism of ALD-HfO2 to protect the MIS-HEMTs from unexpected degradations during X-ray irradiation. Finally, these results emphasize the importance of high-quality dielectric films in MIS-HEMTs to enhance the device performance and safeguard the device under high-energy irradiation, especially in the space environment.

Stable Strained Donor-Free Silanone and Its Derived NHC-Stabilized Disilacyclobutadiene and Cyclic Alkenyl Silylene.

The strained silanone 2 was obtained by the reaction of disilacyclobutene 1 with N2O. Silanone 2 exhibited unprecedented thermal stability in both the solid state and solution. DFT calculations on 2 revealed that the highly polarized Si═O double bond is effectively stabilized by its electron delocalization with the unsaturated Si2C2 ring. Treatment of 2 with 1,3,4,5-tetramethylimidazolin-2-ylidene yielded the first Lewis base-stabilized disilacyclobutadiene 3 via a 1,3-boryl migration. Reaction of 2 with HCCH and Me3SiN3 resulted in the addition of C-H and Si-N bonds to the Si═O double bond. Interestingly, irradiation of 2 at rt yielded oxosilanes 7A and 7B in C6D6 and n-hexane, respectively, via the 1,2-boryl migration and ring expansion, whereas photolysis at -60 °C led to the formation of cyclic alkenyl silylene 8.

The important role of diatomite on multifunctional modified separator of Li-S battery

The commercial applications of lithium-sulfur (Li-S) batteries are limited by decreased cycling performance caused by the shuttle effect of polysulfides, slower kinetic reaction rates, and lithium anode dendrites. This study demonstrates the important role of diatomite (DT) in regulating cycle performance of modified separator for Li-S batteries. A multifunctional separator (Co/NC/DT) with DT as a carrier assembled high loading cobalt nanocluster is prepared. The N-doped carbon is immobilized via Si-N bond between DT and N-doped carbon. The depth profiles of XPS indicate that the ratio of pyrrolic N to pyridinic N of Co/NC/DT reaches 5.31 at the etching of 100 nm versus 0.83 for Co/NC at surface, which suggesting that mainly N species is pyrrolic N after the addition of DT. Theoretical calculations confirm that cobalt nanoclusters grown on pyrrolic N-doped carbon have a lower adsorption energy for active materials compared to that on pyridinic N-doped carbon and can reduce the energy barrier, especially only 0.09 eV for reduction from Li2S6 to Li2S4. In-situ X-ray diffraction analysis confirms Co/NC/DT can effectively promote formation of Li2S. Lithium anode in-situ optical microscopy observation shows the modified separator could reduce lithium dendrites effectively. Li-S battery assembled with the modified separator can reach an initial capacity of 1331.3 mAh g−1 at 0.2 C and cycle 1500 cycles at 1.0 C with a decay of only 0.039% per cycle. Through regulation of DT, Co/NC/DT accelerates the conversion from long-chain sulfur to short-chain sulfur and Li+ transfer rate, resulting in improving cycling performance.

Correlation the microstructure and magnetic properties of Fe-Ni-Mo soft magnetic composites fabricated via polymer-derived ceramics

The coatings play a crucial role in enhancing the performance of soft magnetic composites (SMCs). This study aims to create coatings for Fe-Ni-Mo SMCs using polysilazane (PSZ) as the precursor. The transformation mechanism of the PSZ/resin mixture is studied by analyzing functional groups and chemical bonds at various temperatures. During the self-polymerization process of PSZ at 350 °C, N–H, C = C–H, Si-H bonds, –CH3, and Si-CH3 groups undergo crosslinking reactions to form C–C and Si-N bonds. When the temperature reaches 600 °C, PSZ polymer cleavage, O-Si-C and Si-N-Si bond dominate in the coating. Additionally, PSZ can effectively enhance the heat resistance of silicone resin through its reaction with Si-OH groups, which has a significant effect on increasing the resistivity of SMCs and reducing high frequency core loss. Optimizing the PSZ content to 0.5 wt% enhances the magnetic properties of Fe-Ni-Mo SMCs, resulting in a μe of 74.0 at 100 kHz and a corresponding core loss (Pcv) of 547.7 mW/cm3 at 100 kHz/100 mT. The findings provide valuable insights for optimizing PSZ content to improve magnetic performance in SMCs.

Investigation on the Osteogenic and Antibacterial Properties of Silicon Nitride-Coated Titanium Dental Implants.

The silicon nitride (Si3N4) coating exhibits promising potential in oral applications due to its excellent osteogenic and antibacterial properties. However, a comprehensive investigation of Si3N4 coatings in the context of dental implants is still lacking, especially regarding their corrosion resistance and in vivo performance. In this study, Si3N4 coatings were prepared on a titanium surface using the nonequilibrium magnetron sputtering method. A systematic comparison among the titanium group (Ti), Si3N4 coating group (Si3N4-Ti), and sandblasted and acid-etched-treated titanium group (SLA-Ti) has been conducted in vitro and in vivo. The results showed that the Si3N4-Ti group had the best corrosion resistance and antibacterial properties, which were mainly attributed to the dense structure and chemical activity of Si-O and Si-N bonds on the surface. Furthermore, the Si3N4-Ti group exhibited superior cellular responses in vitro and new bone regeneration and osseointegration in vivo, respectively. In this sense, silicon nitride coating shows promising prospects in the field of dental implantology.

Synthesis and growth mechanism of silicon-based nanostructures from polysiloxane via CVD process

The work is concerned with the deposition of ceramic layers of various morphologies, containing silicon and nitrogen, from a polysiloxane precursor in the chemical vapor deposition (CVD) process. The experiments involved the saturation of nitrogen as a gaseous carrier with polysiloxane molecules in the CVD reaction. Saturated nitrogen was supplied to the reaction zone and depending on the synthesis temperature (1000–1800 °C) and the concentration of resin in gas phase, various nanocrystalline and amorphous deposits were obtained on graphite foil, including polygranulated SiOC powders, fibrous layers composed of nanofibers (NFs) containing silicon and nitrogen, nanochains and composite fibrous components. The morphology, structure and chemical composition of the deposits formed in the CVD reaction changed with increasing temperature. Above 1300 °C, oxygen in the silicon oxycarbide deposits was gradually replaced by nitrogen, creating SiN bonds. The dominant phase in the deposits obtained in the temperature range of 1700–1800 °C were two-phase silicon oxynitride NFs. The core of these NFs consisted of a polycrystalline structure surrounded by an amorphous shell. These structures grew preferentially in the [111] direction through heterogeneous nucleation in the vapor-solid process (VS). The changes in deposits morphology were influenced by the CVD temperature and the resin content in the gas carrier. The activation energy of the crystallization process of silicon oxynitride nanofibers was approximately 96 kJ/mol.

Feasibility of molecular dynamics simulation for process parameter guidance of silicon nitride thin films by PECVD

Due to the limitations of the characterization approaches and the relative complex and expensive characteristics of CVD method itself, experimental-based studies are limited, and simulation of SiNx deposition based on molecular dynamics (MD) simulation provides a more convenient and clear solution. In this work, Tersoff potential function containing the interatomic potential for two-body and three-body interactions was utilized to simulate of the deposition process for SiNx thin films by the PECVD. A quick and accurate method basing on Alpha-shapes was proposed to extract surface atoms and the surface roughness of the thin film samples at substrate temperatures of 353, 493, and 653 K were found to be 0.804, 0.794, and 0.721 nm respectively. By analyzing the radial distribution function, it can get that there are small changes in the Si-Si and Si-N bonds at three temperatures. We also found the diffusion phenomenon at the interface, and the atomic diffusion phenomenon at the substrate interface makes the phenomenon of elemental mutation at the interface less rapid. The simulation results confirm that the substrate temperature during deposition has an effect on the adsorption and atomic drift rate of the substrate, which in turn affects the surface morphology of the film.

From Jekyll to Hyde and Beyond: Hydrogen's Multifaceted Role in Passivation, H-Induced Breakdown, and Charging of Amorphous Silicon Nitride.

In semiconductor devices, hydrogen has traditionally been viewed as a panacea for defects, being adept at neutralizing dangling bonds and consequently purging the related states from the band gap. With amorphous silicon nitride (a-Si3N4)─a material critical for electronic, optical, and mechanical applications─this belief holds true as hydrogen passivates both silicon and nitrogen dangling bonds. However, there is more to the story. Our density functional theory calculations unveil hydrogen's multifaceted role upon incorporation in a-Si3N4. On the "Jekyll" side, hydrogen atoms are indeed restorative, healing coordination defects in a-Si3N4. However, "Hyde" emerges as hydrogen induces Si-N bond breaking, particularly in strained regions of the amorphous network. Beyond these dual roles, our study reveals an intricate balance between hydrogen defect centers and intrinsic charge traps that already exist in pristine a-Si3N4: the excess charges provided by the H atoms result in charging of the a-Si3N4 dielectric layer.

Chemisorption of silicon tetrachloride on silicon nitride: a density functional theory study.

We studied the chemisorption of silicon tetrachloride (SiCl4) on the NH2/NH-terminated silicon nitride slab model using density functional theory (DFT) for atomic layer deposition (ALD) of silicon nitride. Initially, two reaction pathways were compared, forming HCl or NH3+Cl- as a byproduct. The NH3+Cl- complex formation was more exothermic than the HCl formation, with an activation energy of 0.26 eV. The -NH2* reaction sites are restored by desorption of HCl from the NH3+Cl- complexes at elevated temperatures of 205 °C or higher. Next, three sequential ligand exchange reactions forming Si-N bonds were modeled and simulated. The reaction energies became progressively less exothermic as the reaction progressed, from -1.31 eV to -0.30 eV to 0.98 eV, due to the stretching of Si-N bonds and the distortion of the N-Si-N bond angles. Also, the activation energies for the second and third reactions were 2.17 eV and 1.55 eV, respectively, significantly higher than the 0.26 eV of the first reaction, mainly due to the additional dissociation of the N-H bond. The third Si-N bond formation is unfavorable due to the endothermic reaction and higher activation energy. Therefore, the chemisorbed species would be -SiCl2* when the surface is exposed to SiCl4.

Streamlining Si-O bond formation through cobalt-catalyzed dehydrocoupling.

Herein we report a strategy for the synthesis of organosilicons, including siloxanes, silyl ethers, and aminosilanes, via Co-catalyzed dehydrogenative coupling between hydrosilanes and nucleophiles. This discovery represents an expansion of the synthetic toolkit for organosilicon synthesis, forging Si-O and Si-N bonds in the presence of cobalt complexes with salen-type ligands.

Unusual nucleophilic reactivity of a dithiolene-based N-heterocyclic silane.

While the dithiolene-based N-heterocyclic silane (4) reacts with two equivalents of BX3 (X = Br, I) to give zwitterionic Lewis adducts 5 and 8, respectively, the parallel reaction of 4 with BCl3 results in 10, a dithiolene-substituted N-heterocyclic silane, via the Si-S bond cleavage. Unlike 5, the labile 8 may be readily converted to 9via BI3-mediated cleavage of the Si-N bond. The formation of 5 and 8 confirms that 4 uniquely possesses dual nucleophilic sites: (a) the terminal sulphur atom of the dithiolene moiety; and (b) the backbone carbon of the N-heterocyclic silane unit.

Grignard reagents as simple precatalysts for the dehydrocoupling of amines and silanes.

Methyl magnesium bromide is a precatalyst for the dehydrocoupling of silanes and amines to produce aminosilane products under mild conditions. As a commercially available Grignard reagent, this precatalyst represents a simplification over previous magnesium-containing catalysts for Si-N bond formation while displaying similar activity to other magnesium-based catalysts. This observation is consistent with the hypothesis that competitive Schlenk equilibrium can be addressed by not using an ancillary ligand. While the activity of MeMgBr is lower than some reported catalysts, including other commercially available precatalysts, unique selectivity was observed for MeMgBr that may allow for directed synthesis of aminosilane products. This work continues to increase the accessibility of Si-N heterodehydrocoupling through a growing family of commercially available precatalysts that balance activity and selectivity.

Why do life insurers hold sin bonds? Evidence from investment delegation

In recent years, life insurers have increased their exposure to socially controversial (sin) bonds from the alcohol, tobacco, and gaming sectors, which contradicts the social norm constraints commonly associated with such institutional investors. We show empirically that insurers’ investment delegation is associated with a reduced adherence to social norms, evidenced by their investment allocations. We find that insurers who delegate investment decisions to advisors are both more likely to invest and invest higher amounts in sin bonds. The effect is more pronounced when the advisors are unaffiliated with the insurer. Our results offer valuable insights into how investment delegation may affect the impacts of social norms on investment decisions.

In Ukrainian

Thermal destruction of composites of ureaformaldehyde (UPR) and polyester resins (PER) with silicon dioxide nanoparticles having a specific surface area of 280 m2/g, titanium dioxide and titanosilicate with a specific surface area of 40 and 48 m2/g, respectively, when a filler content is no more than 5.0 wt% have been studied. The investigations were performed using The thermally programmed mass spectrometry method with registration of the masses of desorbed atomic fragments in the 10 ‒ 200 m/z range. It was established that during the main polymer mass destruction at 150 ‒ 350 oC, along with low temperature decomposition products, anomalously high thermal resistance of a number of atomic fragments of polymer chains and cross-links are recorded. The atomic composition of destruction fragments and their desorption temperature in the range 400 ‒ 700 oС were determined. It was established that in composites of ureaformaldehyde resin with SiO2 and TiO2 nanoparticles the high temperature resistance of fragments with m/z 27 exhibits due to the formation of strong bonds among the Si and Ti surface sites and the nitrogen atoms of the polymer. Such thermal stability is not realized in resin loading with (Si/Ti)O2 nanoparticles. In composites of polyester resin with silica a high-temperature destruction of oxygen atoms from polyester chains realizes at temperatures of 290 ‒ 400 oC and a low-intensity wide destruction band takes place in the temperature range 400 ‒ 700 oC. In addition, in the temperature range of 400-700 oC cross-links are destroyed with the release of benzene rings and styrene molecules. It was established that anomalously high-temperature desorption is typical for atomic fragments of the polymer structure attached to surface Si and Ti sites through nitrogen or carbon atoms from the polymer structure. Thus, in UPR composites with silicon and titanium oxides, strong chemical nitride bonds of the form Si-N≡C-H and Ti-N≡C-H are formed, which demonstrate anomalously high heat resistance. It is shown that in composites of polyester resin with silicon dioxide nanoparticles, the high-temperature destruction of fragments is due to their desorption from the surface of silicon dioxide particles when breaking their bonds with silicon atoms. Thus, polymer matrices have been determined, in which atomic fragments of the macromolecule, binding to the surface centers of fillers, significantly weaken the thermal destruction of composites due to the formation of strong chemical and coordination bonds.

Robust solid slippery coating for anti-icing and anti-sticking

The slippery liquid-infused porous surface (SLIPS) inspired by the Nepenthes plants has received great attention due to the excellent water-repellency with ultra-low sliding angle. However, the practical application of SLIPS is restricted greatly due to the inevitable loss of lubricant trapped by the micro/nanostructures and the adverse environmental impact of the fluorinated lubricant. Herein, we report a simple and efficient strategy to form a solid slippery coating without loss of lubricant. A commercially available coating with the nominal active constituent of polysilazane (PSZ) was used as the matrix and was slippery with the water sliding angle of approx. 25°. To enhance the water repellency, α, ω- hydroxy silicone oil (HSO) was added into the PSZ solution and the sliding angle of the cured composite coating decreased to approx. 7.0°. The chemical interaction between the Si-H / Si-N bonds of PSZ and the -OH group of HSO produced strong inter-molecular attraction. Acrylic resin was further added to strengthen the overall integrity of the coating and the so-obtained composite coating was durable with no loss of lubricant. Moreover, the curing of PSZ at room temperature was accelerated greatly by HSO from longer than one week to less than one day due to the above-mentioned chemical interactions between the Si-H / Si-N bonds and the -OH group. The solid slippery coating showed promising potential in preventing ice adhesion and anti-sticking to adhesive paper due to its low adhesion properties.

Enhanced holding ability between resin and silanization modified diamonds through sintering Si[sbnd]N bond formation at low temperature

Resin-bonded diamond tools often suffer from poor durability and short lifespan due to the agglomeration of abrasive diamonds and the poor holding ability between diamonds and resin, resulting in diamond detachment during the working process. Modifying the diamond surface is necessary to improve the dispersion of diamonds and the holding ability between diamond and resin. However, common metallic modification methods can cause fine-grained diamonds (FGDs) to agglomerate, and metal plating cannot form a chemical bond with resin at low temperatures for preparing resin-bonded diamond tools. A practical non-metallic method for modifying diamond surfaces was proposed to address these issues, utilizing a silane coupling agent to enhance the binding forces between diamonds and binding agents. A uniform amorphous SiO2 film, with a thickness of 30–40 nm, was developed on FGDs with the hydrolysis and condensation reactions of tetraethylorthosilicate in a water and alcohol mixed solution. The SiO2 layer formed with the CO, CO, and C-O-Si chemical bonds can increase electrostatic repulsion between diamonds, overcoming diamond agglomeration. FGDs modified with SiO2 were combined with phenolic resin and pressed at 170 °C, forming SiN bonds between the resin and SiO2 film and improving the bonding force. Moreover, the SiN bonds can be produced at low temperatures, reducing the risk of diamond detachment during their operation. Hence, the lifespan of modified diamond wheel increase by 22 % than that of pristine diamond wheel. This study provides valuable guidance for developing high-performance, long-lasting, resin-bonded diamond tools.

The Structural and Mechanical Properties of CrAlTiN-Si Nanostructured Coatings Deposited by the Means of High-Power Impulse Magnetron Sputtering

CrAlTiN-Si coatings have demonstrated their ability to prolong the operational life and improve the performance of cutting tools, primarily attributable to their exceptional mechanical, thermal, and tribological properties. Consequently, this investigation focused on the deposition of CrAlTiN-Si coatings utilizing the high-power impulse magnetron sputtering (HiPIMS) technique. The chemical composition, morphology, and microstructure of these coatings, as well as their mechanical and tribological properties, were investigated. The obtained results revealed that the incorporation of silicon into the CrAlTiN matrix significantly influenced the chemical composition, microstructure, and mechanical properties of the coatings. Specifically, silicon contents ranging from 0 to 1.0 at.% led to the formation of a face-centered cubic (fcc) solid solution within the coatings, resulting in a reduction in the lattice parameter from 0.412 nm to 0.409 nm. However, when the silicon content reached 1.9 at.%, a nanocomposite phase comprising an fcc solid solution of CrAlTiSiN and an amorphous phase of SiNx was observed, along with an increase in the lattice parameter from 0.409 nm to 0.413 nm. An XPS analysis confirmed the presence of oxides in all the coatings, but only the sample with a silicon content of 1.9 at.% showed the presence of Si-N bonds. Furthermore, all the coatings exhibited a distinctive cauliflower-type morphology. The nano-hardness testing demonstrated that the incorporation of silicon resulted in coatings with high nano-hardness values, from 20.0 GPa for the sample without silicon to 22.2 GPa when the silicon content was 1.9 at.%. Moreover, as the Si content increased, the presence of silicon contributed to enhancements in the toughness and fracture resistance of the coating.

Group I Alkoxides and Amylates as Highly Efficient Silicon-Nitrogen Heterodehydrocoupling Precatalysts for the Synthesis of Aminosilanes.

Group I alkoxides are highly active precatalysts in the heterodehydrocoupling of silanes and amines to afford aminosilane products. The broadly soluble and commercially available KOt Amyl was utilized as the benchmark precatalyst for this transformation. Challenging substrates such as anilines were found to readily couple primary, secondary, and tertiary silanes in high conversions (>90 %) after only 2 h at 40 °C. Traditionally challenging silanes such as Ph3 SiH were also easily coupled to simple primary and secondary amines under mild conditions, with reactivity that rivals many rare earth and transition-metal catalysts for this transformation. Preliminary evidence suggests the formation of hypercoordinated intermediates, but radicals were detected under catalytic conditions, indicating a mechanism that is rare for Si-N bond formation.

Iron(II)-Catalyzed Activation of Si-N and Si-O Bonds Using Hydroboranes.

We report the activation and functionalization of Si-N bonds with pinacol borane catalyzed by a three-coordinate iron(II) β-diketiminate complex. The reactions proceed via the mild activation of silazanes to yield useful hydrosilanes and aminoboranes. The reaction is studied by kinetic analysis, along with a detailed investigation of decomposition pathways using catecholborane as an analogue of the pinacol borane used in catalysis. We have extended the methodology to develop a polycarbosilazane depolymerization strategy, which generates hydrosilane quantitatively along with complete conversion to the Bpin-protected diamine. The analogous Si-O bond cleavage can also be achieved with heating, using silyl ether starting materials to generate hydrosilane and alkoxyborane products. Depolymerization of poly(silyl ether)s using our strategy successfully converts the polymer to 90% Bpin-protected alcohols.