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  • 1
    ISSN: 1432-0630
    Keywords: 61.72.Cc ; 61.72.Ji ; 73.61.Cw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Vacancy-related defects introduced into n-Si during annealing or aluminium diffusion at high temperature (1000–1250°C) have been studied. Different ambients (argon, nitrogen, vacuum and chlorine-containing atmosphere) were used to create a vacancy supersaturation during heat treatments. Three deep-level centers whose formation is governed by the presence of vacancies have been identified. They were characterized by the following temperature dependences of the thermal emission rate:e3 = 7.92 × 107 T 2 × exp(− 0.455/kT),e 5 = 2.64 × 106 T 2 × exp( − 0.266/kT),e 7 = 7.26 × 106 T 2 × exp (− 0.192/kT). The influence of different factors, such as heat-treatment conditions, concentration of oxygen and doping level in initial crystals, on center formation was studied. An asymmetric diffuseγ-ray scattering was observed near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is related to the formation of structural defects of the vacancy type. In the same region of the crystal, the concentration of the E7 center was one order of magnitude higher than that of other deep-level centers. Comparison of theγ-ray diffraction and deeplevel transient spectroscopy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Russian chemical bulletin 41 (1992), S. 1750-1755 
    ISSN: 1573-9171
    Keywords: vinyl monomers ; radical addition ; reactivity ; correlation schemes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The concept of the apparent electronegativity of a reaction site has been introduced. This has been used to develop a new scheme for calculating the relative rate constants of addition of radicals with different structures to vinyl monomers. The parameters of the scheme are given for 40 reagents. The results of a comparison of calculated and literature rate constants of addition are presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Russian chemical bulletin 42 (1993), S. 640-644 
    ISSN: 1573-9171
    Keywords: vinyl monomers ; radical addition ; MO calculations ; transition states of reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transition states for the addition of.CH3, CH3O.,.CCl3,.CF3, and HOO. radicals to the Cβ and Cα atoms of ethylene, propylene, styrerie, acrylonitrile, methyl acrylate, vinyl acetate, and vinyl- and vinylidene chlorides were calculated using the MNDO method. A satisfactory correlation between the heats of reaction and activation energies was found. The calculated coefficients of proportionality, 0.4–0.5, are twice as high as those in the Polyani—Semenov equation. The calculated heat of reaction of radical addition was shown to be as «strong» an index of reactivity as the calculated activation barrier.
    Type of Medium: Electronic Resource
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