Electronic structure and properties of AlN

The electronic structure of the wurtzite-type phase of aluminum nitride has been investigated by means of periodic ab initio Hartree-Fock calculations. The binding energy, lattice parameters (a,c), and the internal coordinate (u) have been calculated. All structural parameters are in excellent agreement with the experimental data. The electronic structure and bonding in AlN are analyzed by means of density-of-states projections and electron-density maps. The calculated values of the bulk modulus, its pressure derivative, the optical-phonon frequencies at the center of the Brillouin zone, and the full set of elastic constants are in good agreement with the experimental data.

Electronic structure and properties of AlN

The electronic structure of the wurtzite-type phase of aluminum nitride has been investigated by means of periodic ab initio Hartree-Fock calculations. The binding energy, lattice parameters (a,c), and the internal coordinate (u) have been calculated. All structural parameters are in excellent agreement with the experimental data. The electronic structure and bonding in AlN are analyzed by means of density-of-states projections and electron-density maps. The calculated values of the bulk modulus, its pressure derivative, the optical-phonon frequencies at the center of the Brillouin zone, and the full set of elastic constants are in good agreement with the experimental data.

Reseña de Carmen Alén Garabato / Xosé Afonso Álvarez / Mercedes Brea (dirs.) (2010): Quelle linguistique romane au XXIe siècle?. Paris: L"Harmattan, 294 p.

Con la perspectiva que se va abriendo del nuevo siglo tras el transcurso de su primera década, este volumen colectivo reúne un ramillete de contribuciones de distintos especialistas que muestran aspectos diversos de la lingüística románica, disciplina forjada en el xix y que, camino de dos centurias después, induce a los directores-coordinadores del libro en la página inicial de la Présentation a plantear las expectativas de su enseñanza futura en el marco de la ciencia y de la sociedad que vienen.

Alén Garabato, Carmen / Arnavielle, Teddy / Camps, Christian (dir.) (2009): La romanistique dans tous ses états. Paris: L'Harmattan. (Langue et parole)

En aquest volum es recullen les intervencions fetes en el col·loqui La Romanistique dans tous ses états, que tingué lloc a Béziers del 15 al 17 de maig de 2008. El col·loqui s"articulà al voltant de diverses temàtiques, que anaven des de la historiografia de la lingüística romànica fins a les propostes actuals de gestió lingüística (didàctica, protecció de llengües amenaçades), passant per altres temes; tot això, amb el denominador comú de la intenció de fer un estat de la lingüística romànica en un moment en què, si bé és cultivada en institucions diverses i en un esplet de congressos i altres trobades científiques, perd terreny en l"ensenyament universitari, on la perspectiva global i comparatista s"està abandonant.

The effect of substrate on high-temperature annealing of GaN epilayers: Si versus sapphire

We have studied the effects of rapid thermal annealing at 1300¿°C on GaN epilayers grown on AlN buffered Si(111) and on sapphire substrates. After annealing, the epilayers grown on Si display visible alterations with craterlike morphology scattered over the surface. The annealed GaN/Si layers were characterized by a range of experimental techniques: scanning electron microscopy, optical confocal imaging, energy dispersive x-ray microanalysis, Raman scattering, and cathodoluminescence. A substantial Si migration to the GaN epilayer was observed in the crater regions, where decomposition of GaN and formation of Si3N4 crystallites as well as metallic Ga droplets and Si nanocrystals have occurred. The average diameter of the Si nanocrystals was estimated from Raman scattering to be around 3¿nm. Such annealing effects, which are not observed in GaN grown on sapphire, are a significant issue for applications of GaN grown on Si(111) substrates when subsequent high-temperature processing is required.