Elmahjoubi A, Shoker M B, Pagès O, Torres V J B, Polian A, Postnikov A V, Bellin C, Béneut K, Gardiennet C, Kervern G, En Naciri A, Broch L, Hajj Hussein R, Itié J-P, Nataf L, Ravy S, Franchetti P, Diliberto S, Michel S, Abouais A, Strzałkowski K
LCP-A2MC, UR 4632, Université de Lorraine, 57000, Metz, France.
Department of Physics and Materials Science, University of Luxembourg, 41 rue du Brill, 4422, Belvaux, Luxembourg.
Sci Rep. 2023 Sep 4;13(1):14571. doi: 10.1038/s41598-023-39248-6.
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 ZnBe-chalcogenides. The test is done by way of experiment ([Formula: see text]), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations ([Formula: see text] ~ 0-0.5; [Formula: see text]1). The (macroscopic) bulk modulus [Formula: see text] drops below the CdTe value on minor Be incorporation, at variance with a linear [Formula: see text] versus [Formula: see text] 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 ([Formula: see text]0, 0.5) is barely detected experimentally. At large Be content ([Formula: see text]1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular ([Formula: see text]0, 0.5) and inverted ([Formula: see text]~1) Be-Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to CdBeTe without further refinement, albeit in a "relaxed" form. This enhances the model's validity as a generic descriptor of phonons in alloys.
新兴的碲化镉-碲化铍半导体合金在键的共价性和键刚度方面表现出显著的不匹配，这有助于阐明其振动-机械性能，该合金被用作基准来测试渗流模型（PM）的极限，该模型旨在解释相关但对比度较低的锌铍硫族化合物的复杂拉曼光谱。通过实验（[公式：见正文]）进行测试，将拉曼散射与高压下的X射线衍射相结合，并进行从头算计算（[公式：见正文] ~ 0 - 0.5；[公式：见正文]1）。在少量掺入铍时，（宏观）体积模量[公式：见正文]降至低于碲化镉的值，这与从头算预测的线性[公式：见正文]与[公式：见正文]增加情况不符，从而暗示实际晶体中存在较大的非谐效应。然而，在（微观）键尺度上没有异常情况发生，因为从头算预测的少数铍-碲（[公式：见正文]0，0.5）的规则双峰PM型拉曼信号在实验中几乎未被检测到。在高铍含量（[公式：见正文]1）时，相同的双峰信号一直弛豫到反转，这是前所未有的情况。然而，规则（[公式：见正文]0，0.5）和反转（[公式：见正文]~1）的铍-碲拉曼双峰的特定压力依赖性与渗流模型的预测一致。因此，渗流模型无需进一步改进即可直接应用于碲化镉铍，尽管是以一种“宽松”的形式。这增强了该模型作为合金中声子的通用描述符的有效性。
