Study of the chemical reactions' influence on semiconductor films structure formation by the Monte-Carlo method

The investigation by the Monte-Carlo method of the growth of the silicon epitaxial film at a chloride CVD system has allowed to find out the composition of adsorption layer, the micromechanism of the reactions of Si atoms building-in into the growing crystalline layer and the growth conditions influence on the growth rate and film surface roughness. The change of adsorptive layer composition in the system SiCl₄—HCl—H₂ (fraction of adaatoms, silicon atoms built-in a crystal and molecules SiCl₂) depending on temperature has been determined. The change of silicon film growth rate depending on temperature and concentration change of SiH₂Cl₂ has been established and the contribution of growth mechanism (with participation of adatom, silicon atoms and molecules SiCl₂) into the total rate of film growth has been shown.     

Classification of Curves in 2D and 3D via Affine Integral Signatures

We propose new robust classification algorithms for planar and spatial curves subjected to affine transformations. Our motivation comes from the problems in computer image recognition. To each planar or spatial curve, we assign a planar signature curve. Curves, equivalent under an affine transformation, have the same signature. The signatures are based on integral invariants, which are significantly less sensitive to small perturbations of curves and noise than classically known differential invariants. Affine invariants are derived in terms of Euclidean invariants. We present two types of signatures: the global and the local signature. Both signatures are independent of curve parameterization. The global signature depends on a choice of the initial point and, therefore, cannot be used for local comparison. The local signature, albeit being slightly more sensitive to noise, is independent of the choice of the initial point and can be used to solve local equivalence problem. An experiment that illustrates robustness of the proposed signatures is presented.     

Effect of ultrasonic treatment on the molecular weight of carboxymethylated chitin-glucan complex from Aspergillus niger

Different factors affecting the efficiency of the ultrasonic depolymerization of the high-molecular-weight carboxymethylated chitin-glucan prepared from the fungal mycelium of Aspergillus niger have been investigated. The influence of the following parameters was examined: concentration of the chitin-glucan complex, duration of ultrasonic irradiation, reaction temperature and volume of the ultrasonicated solution. The optimized conditions for the efficient ultrasonic depolymerization include: polysaccharide concentration--0.2 mg ml-1; volume of the sonicated solution--25 ml; duration of the sonication--10 min; and constant cooling of the sonicated sample in an ice-water bath.     

Interaction of Phosphorus Iminoilides with Metal Acetates. Crystal and Molecular Structure of Cu[(2-O–)(5-NO2)C6H3N–CH=CH–+PPh3]2 · 2CHCl3

The structure of the Cu[(2-O^–)(5-NO₂)C₆H₃N–CH=CH–⁺PPh₃]₂ complex with the CuN₂O₂ coordination core of distorted square-planar geometry was established by X-ray diffraction analysis. The molecules in the crystal structure of the Cu[(2-O^–)(5-NO₂)C₆H₃N–CH=CH–⁺PPh₃]₂ · 2CHCl₃ solvate are bound via hydrogen bonds of two types, namely, C(sp ²)–H···O and C(sp ³)–H···O.     

Preparation of bisarenechromium π complexes from phenylacetylene and chromium vapors

Conclusion A mixture of isomeric 1,2,4- and 1,3,5-triphenylbenzenes and their complexes with chromium and also organic and organochromium polymers were formed in the reaction of phenylacetylene with chromium vapors under high vacuum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2307–2309, October, 1986.The authors thank S. P. Solodovnikow for recording the EPR spectrum and N. I. Vasyukova for recording the mass spectrum.     

Nucleophilic reactions of polydialkylcyclosilazanes

A study is made of the catalytic condensation polymerization of polydialkylcyclosilazanes [RR'SiNH]_n (n=3,4; R=CH₃, C₂H₅; R'=C₂H₅, C₄H₉, C₆H₁₃, C₉H₁₉) in the presence of small amounts of nucleophilic reagents, to give compounds of the general type R₅R₆'Si₆N₃(NH)₂ and oligomers. The reactivities of polydialkylsilazanes decrease with increase in aliphatic group chain length.     

Geometric and electronic factors in paraffin dehydrogenation on bimetallic platinum catalysts

Summary Relationships between specific activity of bimetallic platinum catalysts in paraffin dehydrogenation and atomic sizes of promoters (i) and enthalpies of alloying with platinum (ii) were considered. The leading role of the size (geometric) effect was demonstrated.     

XX International Chugaev Conference on Coordination Chemistry

Russian Journal of Coordination Chemistry -     

Novel Copolymers of Styrene. 12. Halogen Ring-Substituted Methyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, halogen ring-substituted methyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂CH₃ (where R is 3-Br-4-CH₃O, 5-Br-2-CH₃O, 2-F-5-CH₃, 2-F-6-CH₃, 4-F-3-CH₃, 4-F-3-PhO, 2-F-5-I, 2-F-6-I, 2-F₃C, 4-F₃C) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r ₁) for the monomers is 2-F-5-CH₃ (6.4) > 4-F-3-PhO (5.6) > 4-F₃C (4.8) > 3-Br-4-CH₃O (3.7) > 2-F-5-I (3.6) > 2-F₃C (2.2) > 2-F-6-I (2.1) > 5-Br-2-CH₃O (1.9) > 4-F-3-CH₃ (1.8) > 2-F-6-CH₃ (1.2). Relatively high T _g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500°C range with residue (2–21% wt), which then decomposed in the 500–800°C range.