Exceptional phonon point versus free phonon coupling in ZnBeTe under pressure: an experimental and ab initio Raman study.

Raman scattering and ab initio Raman/phonon calculations, supported by X-ray diffraction, are combined to study the vibrational properties of ZnBeTe under pressure. The dependence of the Be-Te (distinct) and Zn-Te (compact) Raman doublets that distinguish between Be- and Zn-like environments is examined within the percolation model with special attention to x ~ (0,1). The Be-like environment hardens faster than the Zn-like one under pressure, resulting in the two sub-modes per doublet getting closer and mechanically coupled.

Phonon-based partition of (ZnSe-like) semiconductor mixed crystals on approach to their pressure-induced structural transition.

The generic 1-bond → 2-mode "percolation-type" Raman signal inherent to the short bond of common ABC semiconductor mixed crystals with zincblende (cubic) structure is exploited as a sensitive "mesoscope" to explore how various ZnSe-based systems engage their pressure-induced structural transition (to rock-salt) at the sub-macroscopic scale-with a focus on ZnCdSe. The Raman doublet, that distinguishes between the AC- and BC-like environments of the short bond, is reactive to pressure: either it closes (ZnBeSe, ZnSeS) or it opens (ZnCdSe), depending on the hardening rates of the two environments under pressure. A partition of II-VI and III-V mixed crystals is accordingly outlined.

Defect-induced ultimately fast volume phonon-polaritons in the wurtzite ZnMgSe mixed crystal.

Volume-phonon-polaritons (VPP's) propagating at a light-in-vacuum-like speed are identified in the wurtzite-type ZnMgSe mixed crystal by near-forward Raman scattering. Their detection is selective to both the laser energy and the laser polarization, depending on whether the ordinary (n) or extraordinary (n) refractive index is addressed. Yet, no significant linear birefringence (n [Formula: see text] n) is observed by ellipsometry.

Pressure-induced phonon freezing in the ZnSeS II-VI mixed crystal: phonon-polaritons and ab initio calculations.

Near-forward Raman scattering combined with ab initio phonon and bond length calculations is used to study the 'phonon-polariton' transverse optical modes (with mixed electrical-mechanical character) of the II-VI ZnSe1-x S x mixed crystal under pressure. The goal of the study is to determine the pressure dependence of the poorly-resolved percolation-type Zn-S Raman doublet of the three oscillator [1  ×  (Zn-Se), 2  ×  (Zn-S)] ZnSe0.68S0.

Optical characterization of a Cd(0.85)Mg(0.15)Se mixed crystal.

We present an optical characterization of a Bridgman-grown wurtzite-type Cd(0.85)Mg(0.15)Se mixed crystal in the near-band-edge interband transitions using temperature-dependent contactless electroreflectance (CER) and photoreflectance (PR) in the temperature range 15-400 K.