Scientific Reports (Sep 2023)

Vibrational-mechanical properties of the highly-mismatched Cd1−xBexTe semiconductor alloy: experiment and ab initio calculations

  • A. Elmahjoubi,
  • M. B. Shoker,
  • O. Pagès,
  • V. J. B. Torres,
  • A. Polian,
  • A. V. Postnikov,
  • C. Bellin,
  • K. Béneut,
  • C. Gardiennet,
  • G. Kervern,
  • A. En Naciri,
  • L. Broch,
  • R. Hajj Hussein,
  • J.-P. Itié,
  • L. Nataf,
  • S. Ravy,
  • P. Franchetti,
  • S. Diliberto,
  • S. Michel,
  • A. Abouais,
  • K. Strzałkowski

DOI
https://doi.org/10.1038/s41598-023-39248-6
Journal volume & issue
Vol. 13, no. 1
pp. 1 – 11

Abstract

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Abstract The emerging CdTe–BeTe semiconductor alloy that exhibits a dramatic mismatch in bond covalency and bond stiffness clarifying its vibrational-mechanical properties is used as a benchmark to test the limits of the percolation model (PM) worked out to explain the complex Raman spectra of the related but less contrasted Zn1−xBex-chalcogenides. The test is done by way of experiment ( $$x\le 0.11$$ x ≤ 0.11 ), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations ( $$x$$ x ~ 0–0.5; $$x$$ x ~1). The (macroscopic) bulk modulus $${B}_{0}$$ B 0 drops below the CdTe value on minor Be incorporation, at variance with a linear $${B}_{0}$$ B 0 versus $$x$$ x increase predicted ab initio, thus hinting at large anharmonic effects in the real crystal. Yet, no anomaly occurs at the (microscopic) bond scale as the regular bimodal PM-type Raman signal predicted ab initio for Be–Te in minority ( $$x$$ x ~0, 0.5) is barely detected experimentally. At large Be content ( $$x$$ x ~1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular ( $$x$$ x ~0, 0.5) and inverted ( $$x$$ x ~1) Be–Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to Cd1−xBexTe without further refinement, albeit in a “relaxed” form. This enhances the model’s validity as a generic descriptor of phonons in alloys.