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GeSi Raman spectra vs. local clustering/anticlustering: Percolation scheme and ab initio calculations

Abstract : We formalize within the percolation scheme that operates along the linear chain approximation, i.e., at one dimension (1D), an intrinsic ability behind Raman scattering to achieve a quantitative insight into local clustering/anticlustering in an alloy, using GeSi as a case study. For doing so, we derive general expressions of the individual fractions of the six GeSi percolation-type oscillators [1 x (Ge-Ge), 3 x (Ge-Si), 2 x (Si-Si)], which monitor directly the Raman intensities, via a relevant order parameter kappa. This is introduced by adapting to the 1D oscillators of the GeSi-diamond version of the 1D-percolation scheme, i.e., along a fully consistent 1D treatment, the approach originally used by Verleur and Barker for the three-dimensional (3D) oscillators of their 1D-cluster scheme applying to zincblende alloys [H. W. Verleur and A. S. Barker, Phys. Rev. 149, 715 (1966)], a somehow problematic one in fact, due to its 3D-1D ambivalence. Predictive kappa-dependent intensity-interplays between the Ge0.5Si0.5 Raman lines are confronted with existing experimental data and with ab initio Raman spectra obtained by using (32-atom) disordered supercells matching the required kappa values, with special attention to the Ge-Si triplet and to the Si-Si doublet, respectively.
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O. Pagès, R. Hajj Hussein, V. J. B. Torres. GeSi Raman spectra vs. local clustering/anticlustering: Percolation scheme and ab initio calculations. Journal of Applied Physics, American Institute of Physics, 2013, 114 (3), ⟨10.1063/1.4813513⟩. ⟨hal-01517070⟩



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