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  • 1
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance of defects with metastable properties in crystalline GaN (1998)
    Springer
    Physics of the solid state 40 (1998), S. 1648-1652 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An EPR study of GaN revealed the presence of defects exhibiting metastable properties. EPR spectra of two centers (ii1a and ii1b) with axial symmetry along the hexagonal axis of the crystal, which have strongly anisotropic g factors, were observed. The anisotropy of the spectra decreases, and the line shape changes, with increasing temperature. The spectra of the ii1a and ii1b centers disappear at 25 and 50 K, respectively. Subsequent cooling of the samples does not restore the EPR signals, which implies that one observes here phenomena inherent in defects with metastable states. To restore EPR signals, one has to warm the samples to room temperature under very specific conditions. The possible microstructure of the discovered defects is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130626
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  • 2
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance of scandium in silicon carbide (1997)
    Springer
    Physics of the solid state 39 (1997), S. 44-48 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The EPR spectra of scandium acceptors and Sc2+(3d) ions are observed in 6H-SiC crystals containing a scandium impurity. The EPR spectra of scandium acceptors are characterized by comparatively small hyperfine interaction constants, whose values are consistent with the constants for other group III elements in SiC: boron, aluminum, and gallium acceptors. The EPR spectra of scandium acceptors undergo major changes in the temperature interval 20–30 K. In the low-temperature phase the EPR spectra are characterized by orthorhombic symmetry, whereas the high-temperature phase has higher axial symmetry. The EPR spectra observed at temperatures above 35 K and ascribed by the authors to Sc2+(3d) ions, or to the A 2− state of scandium, have significantly larger hyperfine structure constants and narrower lines in comparison with the EPR spectra of scandium acceptors. The parameters of these EPR spectra are close to those of Sc2+(3d) in ionic crystals and ZnS, whereas the parameters of the EPR spectra of scandium acceptors correspond more closely to the parameters of holes localized at group III atoms, in particular, at scandium atoms in GeO2. It is concluded that in all centers the scandium atoms occupy silicon sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130124
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  • 3
    Electronic Resource
    Electronic Resource
    Transition and rare-earth elements in the SiC and GaN wide-gap semiconductors: Recent EPR studies (1999)
    Springer
    Physics of the solid state 41 (1999), S. 783-785 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract EPR studies of transition-element ions in SiC and GaN and of erbium in 6H-SiC are reported. Data are presented on Sc2+ ions and scandium acceptors, and chromium and molybdenum ions in various charge states in SiC. A study was made of nickel and manganese in nominally pure GaN grown by the sandwich sublimation method. The first EPR investigation of Er in 6H-SiC is reported. Erbium was identified from the hfs of the EPR spectra. Various possible models of erbium centers in silicon carbides are discussed. Strong room-temperature erbium-ion luminescence was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130872
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of erbium luminescence in bulk crystals of silicon carbide (2000)
    Springer
    Physics of the solid state 42 (2000), S. 829-835 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The infrared luminescence of Er3+ ions has been studied in bulk crystals of silicon carbide 6H-SiC doped with erbium in the process of their growth. The erbium centers of different symmetry in the crystals are revealed by the EPR technique. A number of intense luminescence bands of erbium ions are observed at a wavelength of about 1.54 µm. The luminescence can be excited by the light with quantum energies above and below the band gap of SiC. It is found that the luminescence exhibits unusual temperature behavior: as the temperature increases, the luminescence intensity abruptly rises starting with 77 K, passes through a maximum at ∼240 K, and, in the vicinity of ∼400 K, decreases down to the values observed at 77 K. The activation energies for the flare-up and quenching of the Er3+ luminescence are estimated at E A ≈130 and ≈350 meV, respectively. The mechanisms of the flare-up and quenching of the Er3+ luminescence in SiC are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1131297
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  • 5
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance of deep boron acceptors in 4H-SiC and 3C-SiC crystals (1998)
    Springer
    Physics of the solid state 40 (1998), S. 31-34 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract EPR spectra of deep boron in 4H-SiC and 3C-SiC crystals have been observed and studied. Two sites in 4H-SiC produced deep-boron EPR signals, quasi-cubic k and hexagonal h. In both cases the deep-boron center symmetry is close to axial along the c crystal axis, and the g factor anisotropy is about an order of magnitude larger than that for shallow boron centers. In the 3C-SiC crystal, the deep-boron symmetry is also close to axial along one of the four 〈111〉 directions. The model proposed for the deep boron center with acceptor properties is BSi-v C, where BSi is the boron substituting for silicon, and v C is the carbon vacancy, with the BSi-v C direction coinciding in 4HSiC with the hexagonal axis of the crystal for both k and h positions. In the cubic 3C-SiC crystal, there are four equivalent deep boron centers, which represent BSi-v C pairs with the bond directed along one of the four 〈111〉 crystal directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130226
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  • 6
    Electronic Resource
    Electronic Resource
    Using a computer to obtain Chebotarev bounds in the nonhomogeneous Minkowski's conjecture (1988)
    Springer
    Journal of mathematical sciences 43 (1988), S. 2624-2635 
    Details
    ISSN: 1573-8795
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The Chebotarev method in Skubenko's form [7] is applied in order to generate by computer improved upper bounds on the product of n real linear nonhomogeneous forms of n variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01727644
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical study of the problem of unsteady heat transfer in a cased-well-bed system (1991)
    Springer
    Journal of engineering physics and thermophysics 60 (1991), S. 645-650 
    Details
    ISSN: 1573-871X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A solution is presented for an unsteady axisymmetric heat-conduction problem connected with the development of the theory of the geothermal logging of cased wells. The solution is used as a basis for reaching several practical conclusions regarding the feasibility of conducting geothermal logging in cased wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00871498
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