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The ability of carbon- and silicon-based nanotubes, including pure carbon, silicon carbide, and Ge-doped silicon carbide nanotubes (CNT, SiCNT, SiCGeNT, respectively), for sensing highly toxic dichlorosilane (H2SiCl2) are investigated using quantum chemistry calculations. The intermolecular interactions between the sensing material and the gas molecule have been investigated with the density functional theory calculations with a functional that includes dispersion terms. The selected method employed is B3LYP-D3 (GD3BJ)/6-311G(d), while other functionals including PBE0, ωB97XD, and M06-2X have been used for comparison. The quantum theory of atoms in molecules (QTAIM) analysis is employed to check the type of intermolecular interactions. Natural bond orbital (NBO) calculations have been used to deduce the bond orders. The findings of this work indicate that the adsorption of the H2SiCl2 is a physisorption process, which is very desirable for its function as a sensing element. The Ge-doped nanotube offers maximum adsorption energy in comparison to CNT and SiCNT.

There is a compelling reason to design cost-effective sensors to detect and measure harmful molecules such as dichlorosilane (H2SiCl2) in the air. In this work, density functional theory (DFT) has been used to study the nature of the intermolecular interactions between the H2SiCl2 gas molecule with a single-walled pristine, Al-doped, and Ga-doped boron nitride nanotubes (BNNT, BNAlNT, and BNGaNT, respectively) to investigate their potential in gas-sensing applications. Full-dimensional geometry optimization and adsorption energies were calculated with four functionals: PBE0, M06-2X, ωB97XD, and B3LYP-D3 with a 6-311G(d) basis set. We find that the B, Al, or Ga atoms provide the most favorable sites for adsorption of the H2SiCl2 molecule. The adsorbate is more tightly bound to the surface of the doped rather than of the pristine BNNT nanotubes, demonstrating a larger energy gain due to adsorption. This is due to the fact that H2SiCl2 interacts with pristine BNNT through weak Van der Waals forces but seemingly has stronger ionic interactions with the doped variants. In general, introducing impurities can improve the selectivity and reactivity of the BNNT toward H2SiCl2. Among all of the absorbents, we find that BNGaNT exhibits the highest affinity toward H2SiCl2, and therefore holds a higher potential compared to the rest of the nanotubes investigated here for designing materials for dichlorosilane sensors.

A dichlorosilane gas and a trichlorosilane gas in ambient hydrogen were evaluated to show their different gas flow motions in a slim vertical cold wall chemical vapor deposition reactor for the Minimal Fab system. This evaluation was performed for improving and controlling the film qualities and the productivities, using two quartz crystal microbalances (QCM) installed at the inlet and exhaust of the chamber by taking into account that the QCM frequency corresponds to the real time changes in the gas properties. Typically, the time period approaching from the inlet to the exhaust was shorter for the trichlorosilane gas than that for the dichlorosilane gas. The trichlorosilane gas was shown to move like plug flow, while the dichlorosilane gas seemed to be well mixed in the entire chamber.

Bisfunctional dichlorosilanes were reacted with tetrasilanol of double-decker shaped octaphenylsilsesquioxane (DDSQ) to form fully condensed DDSQ compounds. The crystallographic and thermal characteristics of these compounds were examined. For compounds capped with dichlorosilanes bearing linear aliphatic moieties, as the number of carbon increases from methyl to n-butyl (from 1 to 4) the melting temperature, Tm, dropped from 546 K to 416 K. While for compounds capped with cycloaliphatic, as the moiety changes from cyclopentyl to cyclohexyl, the value of Tm increases from 533 K to 555 K. Surprising, the highest Tm observed was that when capping was done using diisopropyl dichlorosilane. A Tm of around 565 K was observed, which was even higher as compare to diphenyl dichlorosilane capped DDSQ, which had Tm of about 526 K. Phase behavior of binary and ternary mixtures of these condensed DDSQ was also investigated. To our surprise, mixtures of these compounds form eutectic. The eutectic points were calculated based on ideal binary and ternary eutectic from the thermal properties of pure components. Depending on the crystallography, experimental observations of eutectic match well with calculated values.

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.

The interaction of chlorosilanes and the silicon surface is an important part of reaction processes, such as hydrochlorination and chemical vapor deposition, involved in the production of high purity silicon. We used plane-wave based density functional theory (DFT) to investigate periodic slabs of the Si(100)-c(4 × 2) surface for adsorption of H2, HCl, SiCl2, dichlorosilane (SiH2Cl2 or DCS), trichlorosilane (SiHCl3 or TCS) and silicon tetrachloride (SiCl4 or STC). The effects of surface coverage, molecule orientation, adsorption site and multiple molecule adsorption were studied. All the molecules could undergo dissociative chemisorption in the right orientation and site placement, with HCl and SiCl2 possessing the strongest binding energies. The H2 molecule preferred lower coverage, the HCl molecule was not much affected by coverage while the SiCl2 molecule strongly preferred higher coverage and the STC molecule was affected negatively by both too high or low coverage. The elementary steps leading to transfer of surface crystal silicon atoms to gas phase molecules as part of the chlorination or hydrochlorination process were then looked at through reaction pathway analysis. The formation of SiCl2 from a surface dimer Si atom was found to prefer an intradimer route with a reaction barrier of 3.62 eV (83.48 kcal/mol), going down to 3.10 eV (71.49 kcal/mol) after removal of the first surface Si atom. The subsequent formation of TCS from this SiCl2 was found to have reaction barrier of 1.07 eV (24.68 kcal/mol). STC could also be formed from this SiCl2 molecule with a reaction barrier of 2.86 eV (65.95 kcal/mol).

In the present work SiNx thin films, grown by PECVD technique using dichlorosilane, were used in electroluminescent device (EL) structure. Series of experiments were carried out by varying the flow...

Biphenyl-2,2’-bisfenchyloxydichlorosilane (7, BIFOXSiCl2) is synthesized and employed as precursor for the new silanols biphenyl-2,2’-bisfenchyloxychlorosilanol (8, BIFOXSiCl(OH)) and biphenyl-2,2’-bisfenchyloxysilanediol (9, BIFOXSi(OH)2). BIFOXSiCl2 (7) shows a remarkable stability against hydrolysis, yielding silanediol 9 under enforced conditions. A kinetic study for the hydrolysis of dichlorosilane 7 shows a 263 times slower reaction compared to reference bis-(2,4,6-tri-tert-butylphenoxy)dichlorosilane (14), known for its low hydrolytic reactivity. Computational analyses explain the slow hydrolyses of BIFOXSiCl2 (7) to BIFOXSiCl(OH) (8, Ea = 32.6 kcal mol−1) and BIFOXSiCl(OH) (8) to BIFOXSi(OH)2 (9, Ea = 31.4 kcal mol−1) with high activation barriers, enforced by endo fenchone units. Crystal structure analyses of silanediol 9 with acetone show shorter hydrogen bonds between the Si–OH groups and the oxygen of the bound acetone (OH···O 1.88(3)–2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C–C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12% ee), reaction of 1-chloroisochroman (18) and silyl ketene acetals 11 (up to 85% yield and 5% ee), reaction of chromen-4-one (20) and silyl ketene acetals 11 (up to 98% yield and 4% ee).

The variety of catalysts based on macroporous supported ionic liquid-like phases using chloromethyl styrene cross-linked with divinylbenzene (CMS/DVB) and different NR3 cations was investigated for disproportionation of trichlorosilane in a continuous-flow reactor. To determine the optimal conditions for conducting a complex catalytic process, the primary task is to determine the thermodynamical equilibrium state of the reaction system. Increase in the concentration of DCS in the system occurs from 5 to 10%, which in turn is promising in terms of considering DCS as the main precursor for the processes of epitaxial silicon growth. In addition, the maximum attainable temperature is thermodynamically optimal for the process. In the first stage, the thermal stability of the catalyst supports was determined using evolved gas analysis and all samples have a similar thermal stability 475 К. All samples have been carefully studied by SEM, AFM, EGA and nitrogen physisorption. To compare the catalytic activity of different catalytic systems on the basis of macroporous supports modified by different tritic ammonium functional groups with the subsequent activation, the kinetics of the TCS disproportionation on the catalyst sample having the highest catalytic activity was studied. The results obtained indicate that the introduction of acceptor substituents increases catalytic activity in the disproportionation of TCS. To assess the feasibility of using dichlorosilane (DCS) as a raw material for the creation of semiconductor structures, the kinetics of thermal decomposition of DCS in a mixture with hydrogen was studied at a temperature of 1200–1500 K. According to the obtained kinetic results, the activation energy of the process is determined, which is in the temperature range of 1220–1320 K and the concentration of DCS in hydrogen 9–28.6 mol.%, is 112.9 kJ/mol. Activation energy value indicates the kinetical mode of the thermal decomposition.

Film thickness uniformity is an important index to measure the quality of a deposited layer in selective epitaxial growth (SEG) of silicon using the chemical vapor deposition (CVD) process. The uniformity of a thin film is related to many parameters, such as rotation speed of a wafer, total flow rate, species concentration, susceptor temperature, and operating pressure. Therefore, it is very important to address the problem of coupling multiple parameters and solve the optimization in a computationally efficient manner. In this work, response surface methodology (RSM) is used to analyze the complex coupling effects of different operating parameters on silicon deposition uniformity. Based on the computational fluid dynamics (CFD) model, an accurate RSM model is obtained to predict non-uniformity with different parameters, including temperature, pressure, rotation speed of a wafer, and mole fraction of dichlorosilane (DCS). Analysis of variance (ANOVA) is conducted to determine the statistical significance of each factor in an empirical equation for the expected response. The results of ANOVA analysis indicate the goodness of fit of the regression model. The optimum combination of operating parameters of the problem considered in this study is a susceptor temperature of 1122.2 K, wafer rotation speed of 23.72 rpm, operating pressure of 112 Torr, and DCS mole fraction of 0.01186. The validation tests and optimum solution show that the results are in good agreement with those from the CFD model, and the maximum deviation between the computational solution and predicted values is 2.93%.

Accurate and rapid quantitation of cell attachment, spreading, and growth on a polymer thin film coated glass cover slide was developed by analyzing the digital images of cells stained with dyes. A biodegradable block copolymer poly(ethylene glycol)-block-poly( l -lactide-co-2-methyl-2-carboxyl-propylene carbonate) [PEG-b-P(LA-co-MCC)] was synthesized as model polymer with poly(L-lactic acid) [PLLA] as a control polymer. Only a small quantity of polymer (~5 mg) was needed in this method through dissolving in a solvent and casting on cover slides which were previously modified with dimethyl dichlorosilane (DMDC). Then it was seeded with cells and taken pictures with a digital camera under an optical microscope and analyzed with ImageJ software. Cell number and a series of morphological data were obtained, including cell area, circularity, perimeter and Feret's diameter, etc. The quantitative analysis results indicated that cells preferred to attach and spread on the surface of the copolymer PEG-b-P(LA-co-MCC) compared to PLLA during 24 h of cell culture. This efficient procedure provides a series of convincing statistical data to evaluate the direct interaction between cells and polymers with only an optical microscope, a digital camera and ImageJ software. It's a rapid, economic way for assessing cell affinity and compatibility of novel synthetic polymers by cell culture in vitro.

There is a compelling reason to design cost-effective sensors to detect and measure harmful molecules such as dichlorosilane (H2SiCl2) in the air. In this work, density functional theory (DFT) has been used to study the nature of the intermolecular interactions between the H2SiCl2 gas molecule with a single-walled pristine, Al-doped, and Ga-doped boron nitride nanotubes (BNNT, BNAlNT, and BNGaNT, respectively) to investigate their potential in gas-sensing applications. Full-dimensional geometry optimization and adsorption energies were calculated with four functionals: PBE0, M06-2X, ωB97XD, and B3LYP-D3 with a 6-311G(d) basis set. We find that the B, Al, or Ga atoms provide the most favorable sites for adsorption of the H2SiCl2 molecule. The adsorbate is more tightly bound to the surface of the doped rather than of the pristine BNNT nanotubes, demonstrating a larger energy gain due to adsorption. This is due to the fact that H2SiCl2 interacts with pristine BNNT through weak Van der Waals forces but seemingly has stronger ionic interactions with the doped variants. In general, introducing impurities can improve the selectivity and reactivity of the BNNT toward H2SiCl2. Among all of the absorbents, we find that BNGaNT exhibits the highest affinity toward H2SiCl2, and therefore holds a higher potential compared to the rest of the nanotubes investigated here for designing materials for dichlorosilane sensors.

GeSn/GeSi multi quantum wells with (i) high Sn content, direct bandgap GeSn wells and (ii) GeSi barriers with Si contents in the few %–30% range might be of use in optoelectronics. As GeSn has to be grown in the 300–375 °C range (to avoid Sn segregation/precipitation), GeSi barriers should also be grown in that temperature range, too. GeSi might also be used to passivate, at low temperatures, the surface of Ge-rich imagers and photo-detectors. Thanks to X-Ray Reflectivity (thickness) and X-Ray Diffraction (Si content), I have therefore explored, in a 200 mm Chemical Vapour Deposition tool, the 100 Torr growth of tens of nm thick GeSi layers on Ge(0 0 1) buffers. Precursor gases were Ge2H6 (Ge), SiH2Cl2 and/or Si2H6 (Si). Whatever the chemistry, a temperature increase in the 350–500 °C range resulted in an increase, (a stabilization) then a decrease of the GeSi growth rate. Meanwhile, the Si content increased almost linearly with the temperature. For given Si and Ge flows, GeSi growth rates were higher and Si contents lower with SiH2Cl2 than with Si2H6. Adding SiH2Cl2 to Si2H6 had, quite surprisingly, almost no impact on the GeSi growth kinetics, which was mainly governed by the Si2H6 flow. With high precursor flows, I succeeded in having, with Ge2H6 and SiH2Cl2, GeSi growth rates increasing from 2 up to 32 nm min−1 as the temperature increased from 325 °C up to 375 °C, with a Si content close to 7.5%. Growth rates increased from 0.6 up to 19 nm min−1 and Si contents decreased from 24 down to 22% over the same temperature range with Ge2H6, SiH2Cl2 and Si2H6.

Computer simulations play an important role in determining the optimal design parameters for chemical vapor deposition (CVD) reactors, such as flow rates, positions of the inlet and outlet orifices, and rotational rates, etc. Reliability of the results of these simulations depends on the set of chemical reaction used to represent the process of deposition in the reactor. Aim of the present work is to validate the simple empirical reaction to model the epitaxial growth of silicon for a Dichlorosilane-H 2 (DCS)-H 2 system. Governing equations for continuity, momentum, energy, and reacting species are solved numerically using the finite volume method. The agreement between experimental and predicted growth rates for various DCS flow rates is shown to be satisfactory. The increase in growth rate with the increase in pressure is in accordance with the available data. Based on the validated chemical reaction model, a study was carried out to analyze the uniformity of the silicon layer thickness for two different flow rates in a planetary reactor. It was concluded that, based on the operating conditions, the uniformity of the silicon layer over the wafer is independent of the satellite rotational rate in the reactor.

Bis-phenylethynyl polyhedral oligomeric silsesquioxane (bis-PE-POSS) compounds were synthesized and thermally cured yielding crosslinked materials. After curing at 370 °C, thermal decomposition occurs near 600 °C under nitrogen. These materials were synthesized by condensation of a new phenylethynyl-functional dichlorosilane onto tetrasilanol phenyl POSS, yielding two geometric isomers.

Silicon growth using chemical vapor deposition (CVD) is omnipresent in electronic device technology. CVD reactions of different precursor molecules on Si have been the focus of research for decades. Renewed interest in the CVD growth of silicon films has been spurred by the need for high-quality, ultrathin films for fabrication of novel electronic devices. In this work, we have formulated an experimental nanoscale approach to analyze the modification of wet-prepared Si(0 0 1) surfaces by dichlorosilane (SiH2Cl2, DCS) reactions at low pressure and 500–650 °C performed in a thermal CVD reactor connected to a scanning tunneling microscopy and spectroscopy (STM/STS) system. The DCS dissociation reaction resulted in a decrease of the Si surface potential due to the creation of chlorine-induced electric dipoles. Employing the ability of the scanning tunneling spectroscopy (STS) to recognize specific adsorption sites, we have carried out a comparative analysis of the relative coverage by Cl and Si as a function of exposure conditions. The existence of an intermediate reaction state of the DCS molecule was confirmed by the STS spectra and further supported by Si XPS data and ab initio calculations. This experimental nanoscale approach shows great promise for the CVD growth of ultrathin films.

Pulsed electrical discharges in water were used for nanostructuration of the polysilane-silicon quantum dots (SiQDs) composite dispersed in a cellulose acetate matrix. For this purpose, the polysilane-SiQDs composite was synthesized by chain scission of a poly[diphenyl-co-methyl(H)] oligomer in the presence of molten sodium and catalytic amounts of methyl(H) dichlorosilane. The resulting solid was utilized to prepare free standing thin films using the cellulose acetate matrix as support. Samples of these films were exposed to nanosecond pulsed electrical discharges in water. Through this approach, chemo-mechanical nanostructuration of specific silicon-based structures occurred by removing the excess of polysilane and by oxidative action. Fluorescence measurements of the plasma treated samples showed a higher intensity compared to the untreated ones. The elemental composition and the morphology of the film surface were investigated by TEM, XPS, UHR-SEM and AFM analysis. Such a technique represents a new approach toward a selective processing of the polysilane-SiQDs composite to obtain patterns with different optoelectronic properties on various supports.

A boron-silicon film was formed by chemical vapor deposition at 800 °C and atmospheric pressure using boron trichloride, dichlorosilane and monomethylsilane gases. With the increasing boron trichloride gas flow rate at the fixed dichlorosilane gas flow rate, the deposition rate and the boron concentration decreased and saturated, respectively, following the rate theory assuming the Langmuir-type model. The obtained film was amorphous and dense without any voids. The monomethylsilane and the silicon hydrides, produced by the thermal decomposition of the monomethylsilane gas, were considered to help decomposing the intermediate boron species at the surface. The boron concentrations of 20%–40%, significantly greater than the solubility in the crystalline silicon, were concluded to be obtained using the boron trichloride gas.

Silane has found recent applications in the manufacture of solar photovoltaic cells, which provide solar power economically. One method for the production of silane takes trichlorosilane as a starting molecule, with a reaction mechanism that involves two other intermediate valuable products, dichlorosilane and monochlorsilane. The production system involves a series of reactors and separation steps that can be intensified via reactive distillation. In this work, optimal designs of reactive distillation systems for the production of trichlorosilane, dichlorosilane and silane are developed. Furthermore, a multi-product reactive distillation system for the production of any of these types of silane products is designed. It is shown that an intensified design can be obtained for the production of the three silane products using the same column. The operating conditions at which the columns should be adjusted for the production of each product are reported.

Hot-wall low pressure chemical vapor deposition (LPCVD) of highly crystalline epitaxial thin-film AlN grown on silicon (1 1 1) substrates is reported for the first time. Deposition was carried out in a modified commercial LPCVD at 1000 °C and 2 torr. Preflow time for the aluminum precursor, trimethylaluminum, was varied to nucleate Al, and the resulting variation in X-ray diffraction (XRD) crystalline AlN peaks is presented. With a 30 s dichlorosilane (SiH 2 Cl 2 ) pretreatment at 700 °C and the optimal TMAl preflow time, the FWHM of the resulting film was 1116 arcsec for the AlN (0 0 2) 2 θ - ω peak, and the AlN (0 0 2) peak had an omega rocking curve FWHM of 1.6°. This AlN film was shown to be epitaxially aligned to the Si (1 1 1) substrate.

In this work, we propose a double stack layer design of SiNx/pm-Si thin films by using dichlorosilane in plasma enhanced chemical vapor deposition (PECVD). Adequate deposition condition has been found to attain the average minimal reflectance corresponding to two different layers of SiNx and pm-Si at the suitable refractive index and thickness of the respective films. The average reflectance of the structure is reduced to ∼3% at normal incidence for a wavelength range from 190 to 1100 nm as in comparison to single layer of SiNx thin film structure. Furthermore, using transmission electron microscopy (TEM) presence of double layer stack and formation of silicon quantum dots (QD’s) in the size regime of 3–4 nm has been found. Photoluminescence (PL) diminishment in the double layer structure as in comparison to the single layer of SiNx thin film confirms the effective absorption and total internal reflection induced due to the gradient refractive index. However, visible photoluminescence observed in the present work also remarks the downshift property from the thin film which could subsequently improve the efficiency in silicon solar cells. Present work highlights the prospective of novel structure for downshifting, antireflection and as an passivation coating in new generation of silicon solar cells.

An N-rich silicon nitride film, with a lower refractive index (RI) than the stoichiometric silicon nitride (RI = 2.01), was deposited by alternating the exposure of dichlorosilane (DCS, SiH 2 Cl 2 ) and that of ammonia (NH 3 ) in a plasma-enhanced atomic layer deposition (PEALD) process. In this process, the plasma ammonia was easily decomposed to reactive radicals by RF power activating so that the N-rich silicon nitride was easily formed by excited ammonia radicals. The growth kinetics of N-rich silicon nitride were examined at various deposition temperatures ranging from 400 °C to 630 °C; the activation energy (E a ) decreased as the deposition temperature decreased below 550 °C. N-rich silicon nitride film with a wide range of values of refractive index (RI) (RI = 1.86–2.00) was obtained by regulating the deposition temperature. At the optimal deposition temperature, the effects of RF power, NH 3 flow rate and NH 3 flow time were on the characteristics of the N-rich silicon nitride film were evaluated. The results thus reveal that the properties of the N-rich silicon nitride film that was formed by under plasma-enhanced atomic layer deposition (PEALD) are dominated by deposition temperature. In charge trap flash (CTF) study, an N-rich silicon nitride film was applied to MAONOS device as a charge-trapping layer. The films exhibit excellent electron trapping ability and favor a fresh cell data retention performance as the deposition temperature decreased.

This work reports on the physical and electrical characterization of the oxide/semiconductor interface in MOS capacitors with the SiO2 layer deposited by a high temperature process from dichlorosilane and nitrogen-based vapor precursors and subjected to a post deposition annealing process in N2O. Low interface state density (Dit ≈ 9.0×1011cm-2eV-1) was found at 0.2 eV from EC, which is comparable to the values typically obtained in other lower temperature deposited oxides (e.g., TEOS). A barrier height of 2.8 eV was derived from the Fowler-Nordheim plot, very close to the ideal value expected for SiO2/4H-SiC interface. Basing on these preliminary results, the integration in MOSFETs devices can be envisaged.