On the electronic nature of silicon and germanium based oxynitrides and their related mechanical, optical and vibrational properties as obtained from DFT and DFPT
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AbstractElectronic structure, bonding and optical properties of the orthorhombic oxynitrides Si 2N 2O and Ge 2N 2O are studied using the density function theory as implemented in pseudo-potential plane wave and full-potential (linearized) augmented plane wave plus local orbitals methods. Generalized gradient approximation is employed in order to determine the band gap energy. Indeed, the Si 2N 2O exhibits a large direct gap whereas Ge 2N 2O have an indirect one. Bonding is analyzed via the charge densities and Mulliken population, where the role of oxygen is investigated. The analysis of the elastic constants show the mechanical stability of both oxynitrides. Their bulk and shear modulus are slightly smaller than those reported on nitrides semiconductors due to the oxygen presence. The optical properties, namely the dielectric function, optical reflectivity, refractive index and electron energy loss, are reported for radiation up to 30 eV. The phonon dispersion relation, zone-center optical mode frequency, density of phonon states are calculated using the density functional perturbed theory. Thermodynamic properties of Si 2N 2O and Ge 2N 2O, such as heat capacity and Debye temperature, are given for reference. Our study suggests that Si 2N 2O and Ge 2N 2O could be a promising potential materials for applications in the microelectronics and optoelectronics areas of research. © 2011 Elsevier B.V. All rights reserved.
SponsorsA part of calculations with Wien2k code has been performed in ISCF computers of FUNDP University (Belgium) during the research stays of S. G-S and M. B. K. CASTEP calculations were carried out partially in the Beowulf class heterogeneous computer cluster at KAUST. For the author A. H. R. his work was supported from the institutional research concept of the Institute of Physical Biology, UFB (No. MSM6007665808), the program RDI of the Czech Republic, the project CENAKVA (No. CZ.1.05/2.1.00/01.0024), the grant No. 152/2010/Z of the Grant Agency of the University of South Bohemia and the School of Material Engineering, Malaysia University of Perlis.
JournalComputational Materials Science