Silicon-nitrogen Bond Research Articles

Reversible CO2 insertion into the silicon-nitrogen σ-bond of an N-heterocyclic iminosilane.

The reversible insertion of carbon dioxide into the silicon-nitrogen bond of an N-heterocyclic iminosilane is reported. Solution-phase thermodynamic investigations indicate that this process is thermoneutral and reversible, whereas in the solid-phase CO2 can be stored for extended periods and is only released upon heating to 133 °C.

Intrinsic electron transport in monolayer MoSi2N4 and WSi2N4

We systematically studied the intrinsic electron transport of the recently fabricated two-dimensional (2D) monolayer MoSi2N4 and WSi2N4 (belong to the MA2Z4 family, where M is a transition metal; A is Si or Ge; and Z is N, P, or As) by using the Boltzmann transport theory with the scattering rates calculated from first-principles calculations. It is found that both materials have moderate room temperature electron mobility of 87 cm2/V s for MoSi2N4 and 119 cm2/V s for WSi2N4. Our detailed analysis shows that their electron mobility difference is attributed to the different average effective mass. Moreover, by comparing studies with monolayer MoS2 and WS2, we reveal that the polar optical phonon pattern of MoSi2N4 and WSi2N4 is governed by the antiparallel silicon–nitrogen bond oscillation, different from MoS2 and WS2, in which is governed by the antiparallel transition metal–sulfur bond oscillation. This feature is arising from the large electronegativity difference between N and Si. Nitrogen has the fourth largest electronegativity, so it always tends to attract plenty of electrons from Si and thus Si has a large Born effective charge, thereby resulting in strong Fröhlich interaction. We further found that all the 2D semiconducting MA2Z4 have large Born effective charges, thereby indicating a generally strong electron–phonon coupling strength.

Silicon-nitrogen bond formation via dealkynative coupling of amines with bis(trimethylsilyl)acetylene mediated by KHMDS.

The catalytic synthesis of silylamines mediated by s- and p-block catalysts is largely underdeveloped. Herein, commercially available potassium bis(trimethylsilyl)amide serves as an efficient alternative to transition metal complexes. N-H/Si-C dealkynative coupling was achieved by means of user-friendly main-group catalysis with ample substrate scope and high chemoselectivity.

A review of the R3Si–NH–SiR3–type disilazanes: From synthesis to applications

Disilazanes (e.g., hexamethyldisilazane, tetramethyldisilazane, etc.) are a group of compounds containing a direct silicon-nitrogen bond, which can be easily cleavage and finally resulted in their usefulness as the source of nitrogen (e.g., multicomponent reactions) or silicon (e.g., O–silylation). This review focuses on their synthesis and further applications from the last twenty years. Whilst the use of these disilazanes as silylating agents is well-known, the incorporation of their nitrogen into organic molecules offers immense, but still unexplored opportunities in synthetic chemistry. Last but not least, their indirect involvement in catalysis is also shortly discussed.

Silicon-Nitrogen Bond Formation via Heterodehydrocoupling and Catalytic N-Silylation.

Silicon-nitrogen bond formation is an important subfield in main group chemistry, and catalysis is an attractive route for efficient, selective formation of these bonds. Indeed, heterodehydrocoupling and N-silylation offer facile methods for the synthesis of small molecules through the coupling of primary, secondary, and tertiary silanes with N-containing substrates such as amines, carbazoles, indoles, and pyrroles. However, the reactivity of these catalytic systems is far from uniform, and critical issues are often encountered with product selectivity, conversions, substrate scope, catalyst activation, and in some instances, competing side reactions. Herein, a catalogue of catalysts and their reactivity for Si-N heterodehydrocoupling and N-silylation are reported.

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.

Reactions in silicon-nitrogen plasma.

Reaction mechanisms that lead to creation of silicon-nitrogen bonds are studied in detail. These reactions are of fundamental importance for silicon nitride synthesis by plasma enhanced chemical vapour deposition from the gas mixture of silane (SiH4) and ammonia (NH3). All reactions in SiH4-NH3 plasma can be categorised as some of the basic types of reactions: bond dissociation, neutral nucleophilic substitution, radical neutralisation, neutral-radical addition, silylene addition, silylene rearrangement, radical nucleophilic addition or hydrogen abstraction reaction. Energetics of these reactions is analysed in detail for a great number of reactions belonging to these categories, by using theoretical modelling. Geometry optimisations are carried out with the MP2/aug-cc-pVTZ level of theory and energetics is further determined with high level ab initio calculations at the CASPT2/aug-cc-pVTZ level, which enabled confirmation of relevance of several mechanisms as reactions that lead to silicon nitride growth from plasma enhanced chemical vapour deposition, as well as introduction of new, energetically favourable mechanisms. Besides amine radical assisted eliminative addition and proton transfer reactions, silylene addition reactions are thermodynamically and kinetically favourable since they lack energy barriers. A new reaction pathway for synthesis of silicon nitride from plasma is proposed. This pathway is enabled by the ability of silylene to create two weak dative bonds, which enables silylene-amine complexes to stick to the silicon nitride surface. Upon dissociation of amine from the surface-bound complex, silylene remains on the surface, available for reaction with other reactive species from plasma.

Plasma Nitridation of Hydrogenated Silicon Nitride Film

In this study, chemical-vapor-deposited silicon nitride films were subjected to a novel nitridation process by use of self-biased nitrogen plasma. The film structure and electrical properties such as chemical bonding, surface morphology, dielectric strength, and the capacitance–voltage hysteresis of a metal–insulator–semiconductor device were improved. This was because the hydrogen and oxygen atoms within the silicon nitride film were replaced by the introduced energetic nitrogen atoms. With the optimized self-bias plasma, there were many new silicon–nitrogen bonds formed in the silicon film. These newly formed Si–N bonds reduced the gate leakage of the nitrified device to one order less than that of the non-nitrified device and the dielectric strength can be improved from 7.27 to 9.31 MV/cm.

Nitrogen Enhanced Oxygen Precipitation in Czochralski Silicon Wafers Coated with Silicon Nitride Films

Oxygen precipitation (OP) behaviors were investigated for Czochralski (Cz) silicon wafers, which were coated with silicon nitride (SiNx) films or not, subjected to two-step anneal of 800C/4 h+1000°C/16 h following rapid thermal processing (RTP) at different temperatures ranging from 1150 to 1250C for 50 s. It was found that OP in the Cz silicon wafers coated with SiNx films was stronger in each case. This was because that nitrogen atoms diffused into bulk of Cz silicon wafer from the surface coated SiNx film during the high temperature RTP. Furthermore, it was proved that the RTP lamp irradiation facilitated the in-diffusion of nitrogen atoms, which was most likely due to that the ultraviolet light enhanced the breakage of silicon-nitrogen bonds.

Silicon—Nitrogen Bond Cleavage in N‐(Dimethylimidosilylmethyl)imides and Dimethyl(lactamomethyl)aminosilanes with BF3 Etherate as an Alternative Route to N‐(Dimethylfluorosilylmethyl)imides and Related Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

The study of structure optimization of blast furnace cast steel cooling stave based on heat transfer analysis

The three-dimensional mathematical model of temperature and thermal stress field of cast steel cooling stave in a blast furnace has been modeled. Kinds of the parameters optimization of cast steel cooling stave in a blast furnace are proposed based on the heat transfer analysis. The results indicate that the values of the parameters optimization for a cast steel cooling stave are 200 mm for cooling channels interdistance, 25 mm for inner radius of the water channel, 180 mm for thickness of the cooling stave body, 70 mm for thickness of inlaid brick and 1.5 m/s for speed of cooling water. Reducing the water temperature would be uneconomical. The water temperature can be chosen according to the local conditions. The best choice for lining material is silicon nitrogen bond silicon carbide brick or silicon carbide brick.

Silicon—nitrogen bond cleavage in N-(dimethylimidosilylmethyl)imides and dimethyl(lactamomethyl)aminosilanes with BF3 etherate as an alternative route to N-(dimethylf luorosilylmethyl)imides and related compounds

N-(Dimethylfluorosilylmethyl)succinimide (2a) and N-(dimethylfluorosilylmethyl)phthalimide (2b) were synthesized by the Si—N bond cleavage in readily accessible N-(dimethylimidosilylmethyl)imides with BF3 etherate. Analogously, (O→Si)-chelated 1-(dimethylfluorosilylmethyl)-2-pyrrolidone was prepared from 1-(dimethylmorpholinosilylmethyl)-2-pyrrolidone. X-ray diffraction study demonstrated that the silicon atom in the crystals of 2b is pentacoordinated.

Si-N 코팅막의 기계적 물성 및 구조 분석

Silicon nitride coating films with various ratios of nitrogen to silicon contents were prepared and characterized. The film was coated on silicon substrate by sputtering method with changing nitrogen gas flow rate in a chamber. The nitrogen to silicon ratio was found to have values in a range from 0 to 1.4. Coated film was characterized with scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, nanoindentation scanning probe microscopy, x-ray photon spectrometry, and Raman spectrometry. Silicon nitride phase in all samples showed amorphous nature regardless of N/Si ratio. When N/Si ratio was 1.25, hardness and elastic modulus of silicon nitride film showed maximum with 22 GPa and 210 GPa, respectively. Those values decreased, when N/Si ratio was higher than 1.25 Raman spectrum showed that no silicon phase exist in the film. XPS result showed that the silicon-nitrogen bond was dominant way for atomic bonding in the film. The structure and property was explained with Random Bonding Model(RBM) which was consistent with the microstructure and chemistry analysis for the coating films.

Recent Developments in the Chemistry of Compounds with Silicon—Nitrogen Bonds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Selective synthesis of eight-membered siloxane rings with different substituents on the silicon atoms

The selective synthesis of eight-membered silicon-oxygen rings of the general formula (R 2Si) 2(R′ 2Si) 2O 4 can be achieved using the auxiliary reagent hexabutyldistannoxane. In a first step, the cycles [CH 2–N(R)] 2SiCl 2 [R = tBu ( 1), Ph ( 2)] are reacted with the double molar amount of hexabutyldistannoxane to form [CH 2–N(R)] 2Si(OSnBu 3) 2 3 (R = tBu) and 4 (R = Ph). The syntheses are carried out without any solvent. The distannoxosilanes 3 and 4 are transformed to the eight-membered siloxane rings (R 2Si) 2(R′ 2Si) 2O 4 {R 2 = [CH 2–N( tBu)] 2, R′ = Cl ( 5a), R 2 = [CH 2–N( tBu)] 2, R′ = Br ( 5b), R 2 = [CH 2–N(Ph)] 2, R′ = Me ( 6)} using either SiCl 4, SiBr 4 or Cl 2SiMe 2 as reactants at ambient temperature. The selective cleavage of the silicon–nitrogen bonds in 6 by addition of a solution of HCl in tetrahydrofuran leads to the chloro- and methyl-substituted cyclotetrasiloxane (Me 2Si) 2(Cl 2Si) 2O 4 ( 7). The new cyclotetrasiloxanes 5– 7 have been characterised by spectroscopic methods as well as by single crystal X-ray analyses, revealing Si 4O 4 eight-membered cycles with different substituents on the silicon atoms. Depending on the substitution pattern at silicon atoms, varying Si–O bonds and angle are found. To cite this article: M. Veith et al., C. R. Chimie 6 (2003) 000–000.

Synthesis, structure, and reactivity of some N-phosphorylphosphoranimines.

A large series of new N-phosphorylphosphoranimines that bear potentially reactive functional groups on both phosphorus centers were prepared by silicon-nitrogen bond cleavage reactions of N-silylphosphoranimines. Thus, treatment of the N-silylphosphoranimines, Me(3)SiN=P(Me)(R)X (R = Me, Ph; X = OCH(2)CF(3) and R = Me, X = OPh), with phosphoryl chlorides, RP(=O)Cl(2) (R' = Cl, Me, Ph), readily afforded the corresponding N-phosphoryl derivatives, R'P(=O)(Cl)-N=P(Me)(R)X, in high yields. Subsequent reaction with 1 or 2 equiv of the silylamine, Me(3)SiNMe(2), resulted in ligand exchange at the phosphoryl (P=O) group to give the P-dimethylamino analogues, R'P(=O)(NMe(2))N=P(Me)(R)X (R' = Cl, NMe(2), Me, Ph; R = Me, Ph; X = OCH(2)CF(3), OPh). These new N-phosphorylphosphoranimines (and one thiophosphoryl analogue) were obtained as thermally stable, distillable liquids and were characterized by NMR ((1)H, (13)C, and (31)P) spectroscopy and elemental analysis. One member of the series, Cl(2)P(=O)N=P(Me)(Ph)OCH(2)CF(3) (4), was also studied by single-crystal X-ray diffraction which revealed that the formal P(O)-N single bond [1.55(1) A] is shorter than the formal N=PR(2)X double bond [1.60(1) A]. Such structural features are compared to those of similar compounds and discussed in relationship to the unexpected thermolysis pathways observed for these N-phosphorylphosphoranimines, none of which produced poly(phosphazenes).

Bonding states and electrical properties of ultrathin HfOxNy gate dielectrics

Hafnium oxynitride (HfOxNy) gate dielectric was prepared using reactive sputtering followed by postdeposition annealing at 650 °C in a N2 ambient. Nitrogen incorporation in the dielectric was confirmed by x-ray photoelectron spectroscopy analysis. In comparison to HfO2 of the same physical thickness, HfOxNy gate dielectric showed lower equivalent oxide thickness (EOT) and lower leakage density (J). Even after a high-temperature postmetal anneal at 950 °C, an EOT of 9.6 Å with J of 0.8 mA/cm2 @−1.5 V was obtained. In contrast, J of ∼20 mA/cm2 @−1.5 V for HfO2 with an EOT of 10 Å was observed. The lower leakage current and superior thermal stability of HfOxNy can be attributed to the formation of silicon–nitrogen bonds at the gate dielectric/Si interface and strengthened immunity to oxygen diffusion by the incorporated nitrogen.

Quantum-Chemical Study of the Adducts of Silicon Halides with Nitrogen-containing Donors: II. 1 Calculation of a Donor-Acceptor Bond Energy. Complex trans -SiH 4 ·2NH 3

Structural and thermodynamic characteristics of the trans-SiH4·2NH3 adduct were obtained by ab initio and DFT (RHF and B3LYP) calculations. Scanning the potential energy surface (PES) of the com plex showed that its structure corresponds to a local minimum, whereas the global minimum corresponds to the free fragments. The energy of the silicon-nitrogen chemical bond was calculated with inclusion of fragment rearrangement energies and basis set superposition error. The procedure offered for calculating the Si-N bond energy was extended to adducts of silicon halides with ammonia. It was found that the energy of SiX4 rearrangement contributes most to the energies of donor-acceptor bonds in mono- and diammoniates of silicon tetrahalides.

Synthesis of Boron-Nitrogen-Phosphorus Compounds from N-Silylphosphoranimines

Two modes of reactivity of N-silylphosphoranimines have been utilized to prepare the title compounds containing either B–N=P or Si–N=P–N–B linkages. First, silicon-nitrogen bond cleavage reactions of the N-silylphosphoranimines, Me3SiN=PMe(R)OCH2CF3 (1: R=Me, 2: R=Ph), with various chloroboranes gave the new N-borylphosphoranimines, Ph(Me2N)B–N=PMe2OCH2CF3 (2) and [(Me3Si)2N](Cl)B–N=PMe2OCH2CF3 (10). In other cases, however, the expected B–N=P products were unstable and cyclic phosphazenes [Me(R)P=N]3,4 were obtained. Second, deprotonation-substitution reactions of the aminophosphoranimines, Me3SiN=P(R)Me–N(R′)H, were used to prepare a series of novel (borylamino)-phosphoranimines, Me3SiN=P(R)(Me)–N(R′)–B(NMe2)2 (18: R=Me, R′=t-Bu; 19: R=R′=Me; 20: R=Ph, R′=t-Bu; 21: R=Ph, R′=Me) and Me3SiN=PMe2–N(t-Bu)–B(Ph)X (22: X=NMe2, 23: X=OCH2CF3). All of the new boron–nitrogen–phosphorus products were fully characterized by multinuclear NMR (1H, 13C, and 31P) spectroscopy and elemental analysis.

Structures and energetics of Si3N2 clusters

Mixed clusters of silicon and nitrogen with formula Si3N2 have been investigated at both SCF and MP2 levels of theory. Of eleven stationary points found below 80 kcal/mol, eight correspond to local minima (LM); of these, five are singlet states. Of the triplets, three LM and one transition state (TS) were characterized. The global minimum corresponds to an angular structure with alternating silicon-nitrogen bonds, in contrast with linear ones for other smaller Si/N clusters. A bipyramidal structure 41.0 kcal/mol high in energy can be seen as a natural pattern for tridimensional growing. In general, structures with more SiN bonds are energetically preferred to those in which the SiSi bonds predominate. Attempts to locate TS correlating with the lowest dissociation channels have been unsuccessful due the complex and computationally demanding search. Despite this fact, the thermodynamic stability for structures I, III, IV, and V is guaranteed, being the energy of the lowest channel a lower bound. The atomization energy for the global minimum structure amounts to 420.6 kcal/mol (MP2).