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In this paper, the effect of Cu vacancy of Cu3Si(001) surface for the hydrogenation of silicon tetrachloride was systematically studied by density functional theory (DFT). The favorable adsorption sites and stable configurations of reaction species are obtained and three possible reaction paths of SiHCl3 formation were achieved by transition state search. For the perfect Cu3Si(001) surface(P), Path1 is the most favorable, with a reaction barrier of 158.15 kJ mol−1. For both the single Cu‐vacancy(SV) and double Cu‐vacancy Cu3Si(001) surface(DV), Path2 is the most favorable, with the reaction barriers of 130.07 kJ mol−1 and 124.81 kJ mol−1, respectively. The results reflect that the activation energy of the reaction decreased significantly with the increase of Cu‐vacancy on the Cu3Si(001) surface, which may be the reason for the higher catalytic activity of Cu3Si catalysts with smaller Cu−Si stoichiometric ratios. This study can provide a reasonable explanation for previously experimental observation and provide a guidance for future catalyst design. [ABSTRACT FROM AUTHOR]

Rate coefficients for elementary reactions connected to the potential energy wells of SiHCl3, SiH2Cl2, SiHCl2, and SiH3Cl, which are important Si1 species in chemical vapor deposition (CVD) processes that use chlorosilanes as silicon source gases, were determined through Rice–Ramsperger–Kassel–Marcus (RRKM) theory for various conditions of temperature and pressure. Many of the unimolecular decomposition channels and chemical activation reactions investigated in this work were found to be in the fall‐off regime under subatmospheric to moderately high‐pressure conditions, so that it is expected that accurate modeling of the gas phase in chlorosilane CVD reactors requires careful determination of the rate coefficients as functions of temperature and pressure for the conditions of interest, instead of using high‐pressure limit rate coefficients. The rate coefficients determined here were tabulated using Chebyshev coefficients and can be used in simulations of systems under a wide range of temperature and pressure conditions. [ABSTRACT FROM AUTHOR]

Alkoxychlorosilanes are scientifically and industrially important toward preparing silicone and silica as well as preparation of siloxane-based nanomaterials by stepwise reactions of Si−OR (R=alkyl) and Si−Cl groups. Intermolecular exchange of alkoxy and chloro groups between alkoxysilanes and chlorosilanes (functional group exchange reaction) provides an efficient and environmentally benign route to alkoxychlorosilanes. BiCl3 as a Lewis acid catalyst can promote the functional group exchange reactions more efficiently than conventional acid catalysts. Higher reactivity has been observed for chlorosilanes with smaller numbers of Si−CH3 groups and for alkoxysilanes with larger numbers of Si−CH3 groups. The reaction mechanism is proposed and selective syntheses of alkoxychlorosilanes are demonstrated. These findings also enable us to synthesize an organotrialkoxysilane with four different substituents. [ABSTRACT FROM AUTHOR]

The stabilized Koopmans' theorem (SKT) is very successful in predicting relative vertical electron attachment energies in the Hartree-Fock theory. It is mainly accomplished by systematically scaling the most diffuse functions in the basis set. Recently, the SKT has been extended to the temporary anion states (TASs) of polyatomic molecules in the long-range corrected density functional theory. In this paper, this method will be further applied to chlorosilanes for their importance in the chemical processes of the semiconductor industry. Their resonance energies and lifetimes are determined by computing the density of resonance states via SKT. The detailed characteristics of resonance orbitals are then analyzed. It turns out that the lowest unfilled orbitals of chlorosilanes are essentially σ*Si-Cl in character. Moreover, several TASs with strong Si/Cl 'd' character have been identified. These results, definitely, will help us in understanding the peculiar bonding and chemical properties of chlorosilanes. [ABSTRACT FROM AUTHOR]

Metallurgical purification routes to solar grade silicon have gained a respectable success for the manufacture of standard multicrystalline solar cells. However, gas phase chemically refined silicon (commonly designated as polysilicon) remains unchallenged for semiconductor applications and for the manufacture of monocrystalline solar cells, particularly the most popular high efficiency cell architectures. Therefore, in the medium term future virgin polysilicon should keep a predominant share of the silicon feedstock to electronic and photovoltaic wafers. For photovoltaic to meet the grid parity cost target, significant efforts have been deployed during the past years aiming at drastically reducing the cost of polysilicon. This has been achieved not only through massive capacity expansions but also through simplifying the process as well as developing new gas/solid purification and deposition processes. The replacement of the historical Siemens by the Fluidized Bed Reactor is the most accomplished example of such attempts. Worth noting is also the replacement of chlorine by other halogens in the volatile silicon bearing compound or hydrogen by metal in the deposition/reduction process. However, such cost efficient progress might have been on the expense of the ultimately desirable purity. This contribution will review the most accomplished and promising attempts to develop the polysilicon process. The potential and the limitations of the emerging polysilicon products will be illustrated with respect to their ability to produce high quality wafers for semiconductor or high efficiency solar cells (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The objective of this review is to provide a working knowledge of the chemistry of silicone compounds to the practicing chemist. Although silicone compounds have been known for over 50 yr, the chemistry of these materials remains elusive to the average formulating chemist. This is indeed unfortunate, since the chemistry of the silicon atom and resulting silicone compounds is every bit as wide in scope and rich in content as the chemistry of the carbon atom and the resulting surfactant chemistry upon which it is based. Only in the past decade has the use of silicone as a hydrophobic building block for the preparation of surfactants become common. The recent trend to combine silicone, fatty and polyoxyalkylene moieties in the same molecule has resulted in a plethora of new compounds with new properties. [ABSTRACT FROM AUTHOR]

Nowadays, the quest of new radical precursors based on heteroatom complexes occupies an increasingly prominent position in contemporary research. Herein, we investigated the behavior and the limitations of hexa‐ or pentacoordinated organochlorosilanes and related pentacoordinated silyliums as new families of complexes for the generation of radicals under photocatalytic reductive conditions. Particularly, treatment of chlorophenylbis[N,S‐pyridine‐2‐thiolato(−)]silicon(IV) or the related silylium derivative with the fac‐Ir(ppy)3 (5 mol‐%)/NEt3 (1.5 equiv.) system under blue LEDs irradiation generates a thiopyridyl radical which can participate in the formation of a carbon−sulfur bond by reaction with an allylsulfone. Computational studies supported this experimental finding, and particularly by showing that homolytic fragmentation of C−Ts bond is favored over the fragmentation of thiopyridyl radical. [ABSTRACT FROM AUTHOR]