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Clustering/anticlustering effects on the GeSi Raman spectra at moderate (Ge,Si) contents: Percolation scheme vs. ab initio calculations

Abstract : We test a presumed ability behind the phenomenological percolation scheme used for the basic description of the multi-mode Raman spectra of mixed crystals at one dimension along the linear chain approximation, to determine, via the Raman intensities, the nature of the atom substitution, as to whether this is random or due to local clustering/anticlustering. For doing so, we focus on the model percolation-type GeySi1−y system characterized by six oscillators [Math Processing Error] and place the study around the critical compositions [Math Processing Error] ∼ (0.16, 0.71, and 0.84) corresponding to nearly matching of intensities between the like Raman modes from a given multiplet ([Math Processing Error] triplet or [Math Processing Error] doublet). The interplay between the GeySi1−y Raman intensities predicted by the percolation scheme depending on a suitable order parameter [Math Processing Error] of local clustering/anticlustering is found to be consistent with ab initio calculations of the GeySi1−y Raman spectra done with the Ab Initio Modeling PROgram code using large (64-, 216-, and 512-atoms) disordered cubic supercells matching the required [Math Processing Error] values. The actual “percolation vs. ab initio” comparative insight at moderate/dilute-(Ge,Si) limits, with an emphasis on the [Math Processing Error]-induced intra-bond transfer of oscillator strength, extends a pioneering one earlier achieved at an intermediate composition ([Math Processing Error] ∼ 0.50) by using small (32-atom) supercells [O. Pagès et al., J. Appl. Phys. 114, 033513 (2013)], mainly concerned with the inter-bond transfer of oscillator strength, providing altogether a complete picture.
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Contributor : Olivier Pagès Connect in order to contact the contributor
Submitted on : Thursday, July 16, 2020 - 1:13:50 PM
Last modification on : Thursday, June 10, 2021 - 9:07:41 AM

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V. J. B. Torres, R. Hajj Hussein, Olivier Pagès, M. J. Rayson. Clustering/anticlustering effects on the GeSi Raman spectra at moderate (Ge,Si) contents: Percolation scheme vs. ab initio calculations. Journal of Applied Physics, American Institute of Physics, 2017, 121 (8), pp.085704. ⟨10.1063/1.4976861⟩. ⟨hal-02900706⟩



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