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In situ phosphorus (P)-doped polycrystalline silicon (poly-Si) films by low pressure chemical vapor deposition (LPCVD) were studied in this work for the fabrication of poly-Si passivating contacts. In situ doping was targeted for enabling the full potential of the high-throughput LPCVD technique, as it could allow leaner fabrication of industrial solar cells featuring poly-Si passivating contacts than the more common ex situ doping routes. By careful optimization of the deposition temperature and the flows of the carrier gas (H-2) and the dopant precursor (PH3), high doping in the poly-Si layers was achieved with active P concentrations up to 1.3.10(20) cm(-3) . While reduction in the deposition rate (r(dep)) and thus in the throughput is a known problem when growing in situ P-doped films by LPCVD, this reduction could be limited, and the resulting r(dep) was equal to 0.078 nm/s. The developed poly-Si films were characterized both structurally and in terms of their passivation potential in poly-Si contacts. The latter yielded recombination current densities down to 1.5 fA/cm(2) in passivated (J(0, p)) and 25.6 fA/cm(2) in screen-printing metallized (J(0, m)) regions on saw-damage removed (SDR) Cz-Si surfaces, accompanied by a contact resistivity (rho(c,m)) of 4.9 m Omega.cm(2). On textured Cz-Si surfaces, the corresponding values were J(0, p) = 3.5 fA/cm(2), J(0,m )= 56.7 fA/cm(2), and rho(c,m) = 1.8 m Omega.cm(2). Optical impact of the developed poly-Si films was also assessed and a short circuit density loss of 0.41 mA/cm(2) is predicted per each 100 nm of poly-Si applied at the rear side of solar cells. The authors would like to acknowledge Rajiv Sharma from KU Leuven for his help with the interfacial oxide development, Sukhvinder Singh and Patrick Choulat from Imec for their help with the contact resistivity measurements and sample fabrication, Thomas Nuytten and Stefanie Sergeant from Imec for the Raman spectroscopy measurements, Bastien Douhard and Mustafa Ayyad from Imec for SIMS measurements, Maxim Korytov, Laura Nelissen, and Patricia van Marcke from Imec for the TEM specimen preparation and measurements, and Janusz Bogdanowicz from Imec for his help with the analysis of the Hall measurement data. This work was supported by the European Union’s Horizon2020 Programme for research, technological development, and demonstration [grant number 857793]; and by the Kuwait for the Advancement of Sciences [grant number CN18-15EE-01].

A σ-π extended aryldisilane, comprising a thienopyrazine group as an acceptor fragment and phenothiazine groups as the donor moiety, has been prepared through the introduction of two Si-Si bridges (compound 1). X-ray diffraction analysis determined the crystal structure of 1, and experimental and theoretical approaches investigated its optical properties. Solvatochromic studies revealed the dual emission of 1 in all solvents tested. Compound 1 also exhibited fluorescence in the solid state upon excitation with a hand-held UV lamp, as well as mechanochromic luminescent properties. The packing mode in the crystal structure, variation of phenothiazine conformation, morphological changes between crystalline and amorphous phases are the major factors showing reversible fluorescence under external stimuli. A theoretical conformer study found that 1 exists in distinct conformational groups differing in Gibbs free energy by less than 3 kcal mol-1 . The conformer in the crystalline state of 1 can promote the complete separation of the HOMO and LUMO between the phenothiazine donor and the thienopyrazine acceptor, linked by the disilane linker. HOMO-LUMO energy transition in the crystalline state is forbidden due to the lack of frontier orbital overlap. Crystalline state emission showed LUMO → HOMO-1 transition (locally excited (LE) state). In the amorphous state, the partial presence of quasi-axial conformers allows intramolecular charge-transfer type emission via energy transfer from dominant quasi-equatorial conformers. The strategy proposed in this work provides important guidance for developing stimuli-responsive materials with controlled excited states.

The Mg0 promoted reduction of a sterically hindered 1,6‐dibromohexasilane yielded a cyclopentasilane as the main product. The disilane t‐BuPhHSi‐SiHPht‐Bu was identified as a minor product, which suggests a possible mechanism involving elimination of a transient silylene SiPht‐Bu.

A regioselective and Z-selective three-component silylalkoxylation of 1,3-diene using various alcohols, disilane, and a catalytic Pd/Cu/1,4-benzoquinone/O2 system is established in this Letter. The reaction generates tetra-substituted allyl silanes containing allyl ether moieties in up to 80% isolated yield and on a 1-10 mmol scale via oxidative coupling. A wide variety of substrates, including benzyl alcohol derivates, aliphatic alcohols, and bioactive compounds such as cholesterol, are suitable for use in the developed reaction system.

The present work compares the performance of seven reaction models with respect to a large experimental dataset relevant to the high-temperature pyrolysis of both silane (SiH 4 ) and disilane (Si 2 H 6 ). Their performances were established based on different validation criteria that account for the shape and the amplitude of the validation profile. Then, the model performances were quantified with a global error, which accounts for the experimental uncertainties. The most satisfactory model has a global error as low as 3.1 (i.e., meaning 3.1 times higher than the experimental uncertainty) and the highest fraction (74%) of criteria with a low error ( 2 ), while most of the models have large discrepancies with the validation dataset, global error near 8 and up to 110 for the less accurate model. The origins of these discrepancies are identified with reaction pathway and sensitivity analyses. Among the seven tested model, three main decomposition pathways are evidenced, including one more specific to the models presenting the lowest errors. Based on the global error values, the ability to reproduce all the experimental conditions, and the model analyses, the reaction pathways relevant to the high-temperature pyrolysis of silane and disilane are determined. In addition, the present study provides experimental and numerical guidance for the future developments of silicon hydride reaction models. The limited performance of most of the oldest reaction models may have a significant impact on our current understanding of the pyrolysis and oxidation kinetics of silane.

High-order silane precursors, including trisilane, are candidates for the low-temperature epitaxy process owing to the low energy of Si–Si bond. Higher order silanes are regarded as being more reactive than lower order ones. We compared the SiGe epitaxial growth behaviors of high-order silane precursors on Si substrates in an ultra-high vacuum chemical vapor deposition chamber without a carrier gas. SiGe epitaxial layers with a thickness of 25 nm or more were grown using disilane, trisilane, or tetrasilane precursor at 500 °C. Interestingly, trisilane exhibited more severe island formation than tetrasilane, which has higher reactivity than trisilane, even at lower partial pressure. These islands were not eliminated by lowering pressure but could be suppressed by higher Ge content owing to enhanced surface diffusion.

1,2-Bis-silyl alkenes have exciting synthetic potential for programmable sequential synthesis via manipulation of the two vicinal silyl groups. Transition metal-catalyzed bis-silylation of alkynes with disilanes is the most straightforward strategy to access such useful building blocks. However, this process has some limitations: (1) symmetric disilanes are frequently employed in most of the reactions to assemble two identical silyl groups, which makes chemoselective differentiation for stepwise downstream transformations difficult; (2) the main catalysts are low-valent platinum group transition metal complexes, which are expensive; and (3) internal alkynes remain challenging substrates with low inherent reactivity. Thus, the development of abundant metal-catalyzed bis-silylation of internal alkynes with unsymmetrical disilanes is of significance. Herein, we solve most of the aforementioned limitations in bis-silylation of unsaturated bonds by developing a strongly coordinating disilane reagent and a Ni(0) catalytic system. Importantly, we sufficiently realize the stepwise recognition of the two silyl groups, making this synthetic protocol of wide potential utility., Bis-silylated alkenes offer the advantage of two functional handles with distinguished reactivity for downstream functionalization. Here, the authors report a nickel-catalyzed bis-silylation of internal alkynes to versatile silylated alkene intermediates which can be chemoselectively manipulated.

A novel tetraphenylethylene (TPE) architecture that makes use of a disilane bridge was developed to successfully prepare organic optical power limiting (OPL) materials with high transparency. The σ-bridged TPE derivatives exhibit enhanced solid-state emission efficacies up to 4 times that of TPE. Due to the unique σ-electron delocalization, the incorporated Si–Si bridge gives rise to intense nonlinear optics (NLO) properties. These compounds show favorable optical transparency in the visible region, since the σ–π interaction has a relatively minor effect on the absorption properties of TPE. The poly(bisphenol A carbonate) (PBC) thin films of disilane-bridged compounds exhibit significant reverse saturable absorbance (RSA) responses during Z-scan measurements at 532 nm. In contrast, negligible OPL properties were observed in tetrahydrofuran (THF) solution and when a PBC thin film was prepared with TPE. The disilane-bridged molecular system represents a novel and easily prepared architecture for the construction of solid-state optical limiting materials.

The gas phase reaction of the simplest silicon-bearing radical silylidyne (SiH; X2Π) with disilane (Si2H6; X1A1g) was investigated in a crossed molecular beams machine. Combined with electronic str...

In this paper, selective formation of noncentrosymmetric (Cc; α-crystal) and centrosymmetric (P21/c; β-crystal) 1,1,2,2-tetramethyl-1-(4-(N,N-dimethylamino)phenyl)-2-(2′-cyanophenyl)disilane (1) wa...

Reduction of (boryl)dibromosilane (boryl)SiHBr2 (1; boryl = B(NArCH)2, Ar = 2,6-iPr2C6H3) with 2 equiv of potassium graphite in DME at low temperature led to the isolation of bis(boryl)disilane (bo...

Arylsilanes bearing a bulky alkoxy group on the silicon were synthesized from aryl chlorides and dialkoxydisilanes under reaction conditions utilizing SingaCycle-A3 as a palladium precatalyst and lithium benzoate in wet DMA. This report proposes the first direct and catalytic method for introducing tert-butoxy- or 1-adamantyloxysilyl groups onto various aryl moieties through the silylation reaction.

A formylation of aryl iodides at room temperature using a weaker base KOMe instead of BuLi was developed. The TMS-TMS disilane was discovered to play crucial roles in this formylation. It was found that the MeO− group of KOMe coordinated with two silyl groups of disilane to generate a hypercoordinate silane species. This hypercoordinate silane species reacted with aryl iodide to give an aryl carbanion, which underwent formylation with DMF to give an aryl aldehyde.

The method of chromatography–mass spectrometry is used to study the impurity composition in monosilane obtained in the reaction of magnesium silicide with ammonium chloride in liquid ammonia. To improve the reliability of the impurity identification, along with the study of pure monosilane samples, we analyzed monosilane fractions isolated upon purification by low temperature rectification. To separate the impurities of permanent gases, hydrocarbons C1–C3, volatile inorganic hydrides, disilane, and alkylsilanes, we used an adsorption capillary column GS-GasPro 60 m × 0.32 mm with a modified silica gel. To separate the homologs of monosilane, siloxanes, and alkylsilanes, we used a column 25 m × 0.26 mm, df = 0.25 μm with a polytrimethylsilylpropyne (PTMSP) sorbent. The impurities were identified by comparison of their experimental mass spectra with the NIST database. In the absence of the mass spectra of analytes in the NIST electronic database or in the case of their low coincidence with the database spectra, the identification was performed using mass spectra and retention times published in the literature. The impurities of permanent gases, carbon dioxide, hydrocarbons C1–C3, volatile inorganic hydrides, monosilane homologies, siloxanes, and alkyl silanes were identified in monosilane. Quantitative determination of the impurities was carried out in the mode of selective ion detection using the mass numbers for which the signal-to-noise ratio was maximal. Their concentrations were calculated using a method of absolute calibration by the peak areas; in the case where reference samples were absent, the concentrations were determined using the dependence of the sensitivity coefficients of their detection on the magnitude of the total ionization cross sections. The detection limits of the impurities range within 1 × 10–5–2 × 10–7 mol %. The accuracy of the analysis was verified by the method of sample size variation. The results of determination of the impurities in monosilane after synthesis, as well as in monosilane purified by low temperature rectification and in the isolated fractions with concentrated higher and lower boiling impurities, are reported.

Silane (SiH4) plasmas are widely used for the deposition of hydrogenated amorphous silicon (a-Si:H) films. Nevertheless, the chemical processes governing film deposition are still incompletely understood. Moreover, there is still no general method available to determine the absolute concentration of the silyl radical (SiH3), which is the accepted chemical precursor of a-Si:H films. In this study, a 10% silane in helium RF plasma was spectroscopically investigated between 2085 and 2175 cm-1 using an external cavity quantum cascade laser (EC-QCL) based spectrometer. This led to the identification of 4 distinct species from their absorption features: SiH4, disilane (Si2H6), SiH3, and an unassigned short-lived species. Furthermore, 17 absorption features of SiH3 were identified and unambiguously assigned. Fast spectral scanning of selected absorption features belonging to the four species in a 10 Hz pulsed RF plasma enabled the measurement and interpretation of their temporal behavior in terms of plausible chemical reactions involving silicon containing species. By quantitatively measuring the decay of the SiH3 a ← a pP4 (5) transition at 2151.3207 cm-1 after the discharge was stopped, its line strength (S) was determined to be (7.5 ± 5.5) × 10-20 cm2 cm-1 mol-1.

The increased synthetic utility of organosilanes has motivated researchers to develop milder and more practical synthetic methods. Silylzinc reagents, which are typically the most functional group tolerant, are notoriously difficult to synthesize because they are obtained by a pyrophoric reaction of silyllithium, particularly Me3SiLi which is itself prepared by the reaction of MeLi and disilane. Furthermore, the dissolved LiCl in silylzinc may have a detrimental effect. A synthetic method that can avoid silyllithium and involves a direct synthesis of silylzinc reagents from silyl halides is arguably the simplest and most economical strategy. We describe, for the first time, the direct synthesis of PhMe2SiZnI and Me3SiZnI reagents by employing a coordinating TMEDA ligand, as well as single crystal XRD structures. Importantly, they can be obtained as solids and stored for longer periods at 4 °C. We also demonstrate their significance in cross-coupling of various free alkyl/aryl/alkenyl carboxylic acids with broader functional group tolerance and API derivatives. The general applicability and efficiency of solid Me3SiZnI are shown in a wide variety of reactions including alkylation, arylation, allylation, 1,4-addition, acylation and more., The first direct synthesis of PhMe2SiZnI and Me3SiZnI reagents from silyl iodides is described. They can be obtained as solids and stored at 4 °C for extended periods. The versatility of solid Me3SiZnI is demonstrated in a variety of reactions.

A disilane that contains two diphenylphosphino moieties, (Ph2PCH2)Ph2Si-SiPh2(CH2PPh), was readily synthesized from the reaction of ClPh2Si-SiPh2Cl with (tmeda)Li(CH2PPh2). Treatment of the thus-obtained disilane with the palladium(0) precursor [Pd(CNtBu)2]3 led to the exclusive formation of a trinuclear palladium cluster in which three palladium atoms are arranged in a triangular fashion. Single-crystal X-ray diffraction analysis of the obtained triangular cluster revealed that novel silylphosphido chelating ligands were formed via a skeletal rearrangement of the ligand framework.

Herein, a readily available disilane Me3SiSiMe2(OnBu) has been developed for the synthesis of diverse silacycles via Brook- and retro-Brook-type rearrangement. This protocol enables the incorporation of a silylene into different starting materials, including acrylamides, alkene-tethered 2-(2-iodophenyl)-1H-indoles, and 2-iodobiaryls, via the cleavage of Si–Si, Si–C, and Si–O bonds, leading to the formation of spirobenzosiloles, fused benzosiloles, and π-conjugated dibenzosiloles in moderate to good yields. Preliminary mechanistic studies indicate that this transformation is realized by successive palladium-catalyzed bis-silylation and Brook- and retro-Brook-type rearrangement of silane-tethered silanols., A readily available disilane Me3SiSiMe2(OnBu) as a silylene source has been developed for the synthesis of diverse silacycles via Brook- and retro-Brook-type rearrangement.

Conventional Si or SiGe epitaxy via chemical vapor deposition is performed at high temperatures with a large amount of hydrogen gas using silane (SiH4) or dichlorosilane (SiCl2H2) precursors. These conventional precursors show low growth rates at low temperatures, particularly below 500 °C although a low thermal budget becomes more important for modern fabrication techniques. High-order silane precursors, such as disilane, trisilane, and tetrasilane, are candidates for low-temperature epitaxy due to the lower strength of the Si-Si bonds compared to that of the Si-H bonds. In addition, the consumption of vast amounts of hydrogen gas is an additional burden of the low-temperature process due to its low throughput. In this study, we explored Si and SiGe epitaxial growth behaviors using several high-order silanes under ultra-high vacuum chemical vapor deposition (UHVCVD) and low-pressure chemical vapor deposition (LPCVD) conditions without a carrier gas. Disilane showed high-quality epi-growth under both pressure conditions, whereas trisilane and tetrasilane showed enhanced growth rates and lower quality.

Density functional theory (DFT) calculation has been used to reveal the mechanism of the Pd-catalyzed disilylation reaction of aryl halides. The DFT calculations indicate that the reaction starts with the oxidative addition of the C–I bond to the Pd(0) catalyst. Concerted metalation–deprotonation (CMD) can then generate a five-membered palladacycle. Insertion of Pd(II) into the Si–Si bond in disilane followed by two sequential steps of reductive eliminations yields the disilylation product and regenerates the Pd(0) catalyst. According to the NPA charge analysis along the reaction coordinates, the formal oxidative addition of the Si–Si bond to palladium could be considered as the insertion of palladium into the Si–Si bond. However, the conventional oxidative addition of the C–I bond to palladium is exactly an oxidation process with the electron transfer from the palladium atom to the C–I bond. Therefore, electron rich Pd(0) is beneficial for the oxidation process, and Pd(II) prone to acquire electrons is beneficial for the insertion process.

The industry‐scale production of methylchloromonosilanes in the Müller–Rochow Direct Process is accompanied by the formation of a residue, the direct process residue (DPR), comprised of disilanes MenSi2Cl6‐n (n=1–6). Great research efforts have been devoted to the recycling of these disilanes into monosilanes to allow reintroduction into the siloxane production chain. In this work, disilane cleavage by using alkali and alkaline earth metal salts is reported. The reaction with metal hydrides, in particular lithium hydride (LiH), leads to efficient reduction of chlorine containing disilanes but also induces disproportionation into mono‐ and oligosilanes. Alkali and alkaline earth chlorides, formed in the course of the reduction, specifically induce disproportionation of highly chlorinated disilanes, whereas highly methylated disilanes (n>3) remain unreacted. Nearly quantitative DPR conversion into monosilanes was achieved by using concentrated HCl/ether solutions in the presence of lithium chloride., Too valuable for disposal or incineration: Simple recycling of the Müller–Rochow Direct Process residue with LiH yields monosilanes suitable for the reintroduction into the silicone production chain.

In the present study, SiO2 was deposited using the atomic layer deposition (ALD) with a 1,2-bis(diisopropylamino)disilane (BDIPADS) precursor. The use of this precursor exhibited a higher growth rate and lower initial growth temperature than the use of diisopropylaminosilane (DIPAS) did. The ALD reaction using BDIPADS produced SiO2 with excellent quality owing to the self-catalytic reaction between the amine ligand and O3; therefore, the SiO2 film has no impurities. When the growth temperature was increased gradually, the stoichiometry and density of SiO2 were improved also because the reaction between surface adsorbate species was nearly complete. ALD SiO2 exhibited a higher dielectric constant than the bulk SiO2 did, from the metal-oxide-semiconductor capacitor, because of the incorporated hydroxyl groups in the film. Furthermore, the etching characteristics were modulated by changing the growth temperature to ensure that the film can be used as a hard mask for lithography. From the DFT calculation, high reaction energy between the BDIPADS and Si–OH was observed. Moreover, the Si–Si cleavage results in the existence additional reaction sites, such as amine group, allowing low-temperature growth and enhanced productivity. Therefore, the number of Si atoms in a molecule affects the growth rate and initial growth temperature to ensure that BDIPADS is a highly excellent precursor for the SiO2 deposition; therefore, its use can lead to a remarkably high productivity.

Modern approaches to understanding the origin of the internal rotation barrier in ethane and its analogs were reviewed. Computer simulation revealed the inversion of the relative stability of the staggered and eclipsed forms of such compounds in the cavity of nanotubes. Conformational behavior of disilane, methanol, methylmercaptan, hydroxyborane, diborane, and hydrazine molecules in nanotubes was also examined. It was concluded that the orbital interactions energy constitutes an important contribution to stabilization of the staggered form of ethane and its analogs.

International audience; Azasilines fused nitrogen heterocycles are prepared in excellent yields (from 74 to 98 % according to the structures) for the first time in one operation with high regio‐ and stereoselectivities. The key step consists of an intramolecular palladium‐catalyzed cyclisation reaction of heteroaryl disilane cores, bearing double or triple bond. We first studied the reactivity of pyridyl heterocycles, using xylenes as solvent and Pd(dba)2‐P(OEt)3 as catalyst at 130 °C. The Z configuration of the adducts suggested that the reaction proceeds following a syn addition on the alkyne. This strategy has then been illustrated by the synthesis of complex polyheterocyclic scaffolds (phenothiazine, indole, carbazole, quinoline and tetrahydroquinoline) starting from other nitrogen heteroaryl compounds, to demonstrate the potential of the process, in order to obtain promising biological scaffolds.

The efficient modification of zeolites for improving their catalytic properties is a significant subject of microporous materials chemistry. H-ZSM-5 zeolite is a potent catalyst of the production of propylene as an important start material of a variety of chemical products, which is mainly obtained from fossil resources. Recently, the production of propylene using non-fossil carbon resources are desired because of the depletion risk of fossil fuels and global warming problem. Dimethyl ether (DME) conversion to propylene is actively studied using acid catalysts as an alternative synthetic route of propylene. This paper reports the propylene production from DME using H-ZSM-5 catalyst whose surface was modified with an organo-disilane compound, 1,4-bis(hydroxydimethylsilyl)benzene. An H-ZSM-5 catalyst surfacely modified with the disilane compound produced propylene from DME in higher yield than original (non-modified) H-ZSM-5. Air flow treatment at 480 °C effectively regenerated the modified H-ZSM-5 that was deactivated by coke formation during the reaction, and this regenerated catalyst had a nearly equivalent activity of the propylene production to the catalyst before deactivation. The polycyclic aromatic compounds formed from the benzene ring of the disilane compound that covered the exterior surface of H-ZSM-5 controlled the catalytic activity to increase the yield of propylene.