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Wyszukujesz frazę "Majewski, J" wg kryterium: Wszystkie pola

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    Wyświetlanie 1-5 z 5
    Tytuł:
    Density Functional Studies of Nonlinear Elastic Properties for Zinc-Blende Nitrides
    Autorzy:
    Łopuszyński, M.
    Majewski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047721.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.20.Dc
    43.25.+y
    62.50.+p
    Opis:
    In this paper we present a method of calculating third-order elastic constants C$\text{}_{ijk}$ and its application to zinc-blende nitrides AlN, GaN, and InN. Our approach is based on accurate ab initio calculations of both energy and stress as a function of applied strain. Ab initio computations are performed within density functional theory framework. To assess the reliability of the presented method, we compare our theoretical findings for GaAs with experimental results for C$\text{}_{ijk}$ available for this material.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 443-447
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pressure Dependence of Elastic Constants in Zinc-Blende III-N and Their Influence on the Light Emission in Nitride Heterostructures
    Autorzy:
    Łepkowski, S. P.
    Majewski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2038098.pdf
    Data publikacji:
    2004-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.20.Dc
    62.50.+p
    Opis:
    We studied the nonlinear elasticity effects for the case of III-N compounds. Particularly, we determined the pressure dependences of elastic constants, in zinc-blende InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We found significant and almost linear increase in C$\text{}_{11}$, C$\text{}_{12}$ with pressure for considered nitrides compounds. Much weaker dependence on pressure was observed for C$\text{}_{44}$. We also discussed pressure dependences of two-dimensional Poisson's ratio and elastic anisotropy coefficient. Finally, we showed that the pressure dependence of elastic constants results in significant reduction of the pressure coefficient of the energy emission in cubic InGaN/GaN quantum wells and essentially improves the agreement between experimental and theoretical values.
    Źródło:
    Acta Physica Polonica A; 2004, 105, 6; 559-566
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Nonlinear Elasticity and Electromechanical Coupling on Optical Properties of InGaN/GaN and AlGaN/AlN Quantum Wells
    Autorzy:
    Łepkowski, S. P.
    Majewski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2046928.pdf
    Data publikacji:
    2006-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.De
    62.20.Dc
    77.65.-j
    Opis:
    We present theoretical studies of effects of the nonlinear elasticity and the electromechanical coupling on the optical properties of InGaN/GaN and AlGaN/AlN quantum wells. In these structures, due to the lattice misfit between constituents, the quantum wells are compressively strained and the intrinsic hydrostatic pressure is present. Therefore, the nonlinear elasticity is investigated by taking into account the pressure dependence of elastic stiffness tensor for the strained quantum wells. We show that this effect leads to (i) decrease in the volumetric strain and (ii) increase in the polarization-induced built-in electric field in the quantum wells. Consequently, the interband transition energies in the quantum wells decrease when the nonlinear elasticity of nitrides is considered. On the other hand, we show that the effect of electromechanical coupling, i.e., co-existence of ordinary and converse piezoelectric effects results in increase in the interband transition energies in the considered quantum wells. It turns out that the influence of the nonlinear elasticity on the optical properties is stronger than the influence of electromechanical coupling for InGaN/GaN quantum wells, while for AlGaN/GaN the opposite situation is observed.
    Źródło:
    Acta Physica Polonica A; 2006, 110, 2; 237-242
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Theoretical Calculations of Cohesive and Electronic Properties of Quaternary AlGaInN Alloys
    Autorzy:
    Łopuszyński, M.
    Bartoszek, J.
    Majewski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047722.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.66.Dk
    61.66.-f
    62.20.Dc
    64.30.+t
    Opis:
    We present theoretical studies of the AlGaInN nitride quaternary alloys. The studies are based on ab initio calculations performed within the density functional theory and virtual crystal approximation. The equilibrium lattice constants, bulk moduli, and elastic constants were calculated for the whole possible range of concentrations of the alloy constituents. The theoretical values were then fitted with second- and third-order polynomials. For all properties studied, the considerable bowing was observed.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 449-454
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nonlinear Elasticity in Wurtzite GaN/AlN Planar Superlattices and Quantum Dots
    Autorzy:
    Łepkowski, S. P.
    Majewski, J. A.
    Jurczak, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/2044495.pdf
    Data publikacji:
    2005-11
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.-n
    62.20.Dc
    62.50.+p
    Opis:
    The elastic stiffness tensors for wurtzite GaN and AlN show a significant hydrostatic pressure dependence, which is the evidence of nonlinear elasticity of these compounds. We have examined how pressure dependence of elastic constants for wurtzite nitrides influences elastic and piezoelectric properties of GaN/AlN planar superlattices and quantum dots. Particularly, we show that built-in hydrostatic pressure, present in both quantum wells of the GaN/AlN superlattices and GaN/AlN quantum dots, increases significantly by 0.3-0.7 GPa when nonlinear elasticity is used. Consequently, the compressive volumetric strain in quantum wells and quantum dots decreases in comparison to the case of the linear elastic theory. However, the z-component of the built-in electric field in the quantum wells and quantum dots increases considerably when nonlinear elasticity is taken into account. Both effects, i.e., a decrease in the compressive volumetric strain as well as an increase in the built-in electric field, decrease the band-to-band transition energies in the quantum wells and quantum dots.
    Źródło:
    Acta Physica Polonica A; 2005, 108, 5; 749-754
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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