Non-random Be-to-Zn substitution in ZnBeSe alloys: Raman scattering and ab initio calculations

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2010-02, Vol.73 (4), p.461-469
• Main Authors: Pagès, O., Postnikov, A. V., Chafi, A., Bormann, D., Simon, P., Glas, F., Firszt, F., Paszkowicz, W., Tournié, E.
• Format: Article
• Language: English
• Subjects: Alloys; Chemical Sciences; Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Epitaxy; Exact sciences and technology; Fluid- and Aerodynamics; Iii-v and ii-vi semiconductors; Infrared and raman spectra and scattering; Lattice dynamics; Material chemistry; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Physics and Astronomy; Raman spectroscopy; Solid State and Materials; Solid State Physics; Specialty metals industry; Toy industry; Vibration; Zinc
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2010-00047-0

We show how the 1-bond ↦ 2-mode percolation behaviour, as observed in the transverse optical (TO) Raman spectra of several A 1-x B x C semiconductor (SC) alloys, can be used to detect and to estimate a possible deviation from randomness in the A↔B substitution. As a case study we focus on the Zn 1-x Be x Se system, which shows an uniquely well-resolved percolation-type TO fine structure in the spectral range of Be–Se vibrations, and discuss differences in the Be–Se Raman signals from bulk crystals and epitaxial layers. In the epilayers, the longer (shorter) Be–Se bonds from the BeSe-like (ZnSe-like) region appear to be slightly but systematically over- (sub-) represented with respect to the random case. This indicates a trend towards local ordering in analogy with the known case of InGaP 2 . The discussion is supported by ab initio insight into the phonon/bond length properties of a prototype ZnBeSe supercell at x ~ 0.5 in their dependence on the amount of CuPt ordering (the most frequent type of spontaneous ordering). Besides, the ab initio calculations reveal some singularity in the lattice dynamics/relaxation around the intermediate value of the order parameter η ~ 0.5, coinciding with the so far experimentally achievable limit of CuPt spontaneous ordering.