Percolation behavior in the Raman spectra of ZnBeTe alloy

Pagès, O.; Tite, Teddy; Bormann, D.; Maksimov, O.; Tamargo, M. C.

doi:10.1063/1.1467711

Cited by 30 publications

(32 citation statements)

References 12 publications

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“…Altogether this might explain why random Zn 1−x Be x ͑Se, Te͒ mixed crystals of high quality, regarding x-ray measurements, can be formed over wide composition ranges. 4,5 In particular, the full range is available with ZnBeSe, while the Be content is limited to ϳ0.5 in ZnBeTe. This offers much interesting opportunity for detailed investigation of percolation effects upon the physical properties of the stiff Be-VI bond.…”

Section: Introductionmentioning

confidence: 99%

Long-wave phonons inZnSe−BeSemixed crystals: Raman scattering and percolation model

et al. 2004

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We extend to longitudinal-optical (LO) phonons the percolation model set for the basic understanding of the atypical transverse-optical (TO) one-bond→ two-mode behavior observed by Raman scattering in the Be-Se spectral range of the random Zn 1−x Be x Se alloy ͑0 ഛ x ഛ 1͒, which opens the class of mixed crystals with contrast in the bond stiffness. The study is supported by contour modeling of the TO and LO Raman line shapes. This is achieved via application of the Hon and Faust treatment to a version of the modified-randomelement-isodisplacement model generalized to multioscillators. While the TO signal clearly discriminates between Be-Se vibrations within the hard Be-rich region and the soft Zn-rich one, complexity arises in the LO symmetry due to vibration coupling via the 1ong-range longitudinal polarization field. In particular this generates a massive transfer of oscillator strength from the low-frequency ͑LO − ͒ (hard, soft)-mixed mode to the high-frequency ͑LO + ͒ one, which results in an apparent LO + single-mode behavior. Moreover the contrasts between the Zn-Se and Be-Se bond lengths and bond stiffness are proposed to force a Verleur and Barker-like (VB) discrete multimode Raman response from each region. Accordingly LO − and LO + intramode transfers of oscillator strength superimpose to the LO − → LO + intermode one. This accounts for the spectacular distortions of the LO + line shape. On the whole, the puzzling LO behavior can be regarded as the result of a cooperative phenomenon between two discrete assemblies of polar LO phonons, driven by the long-range longitudinal polarization field. Also, the Verleur and Barker description accounts for subtle unexplained behaviors in the TO symmetry. More generally it appears to provide a much attractive area for the discussion of the asymmetries of the TO and LO Raman line shapes in random alloys, as a possible alternative to the much debated spatial correlation model or to internal/external strain effects.

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Section: Introductionmentioning

confidence: 99%

Long-wave phonons inZnSe−BeSemixed crystals: Raman scattering and percolation model

et al. 2004

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“…3͒, even at larger substitution of 14%. 8 At this stage it is feared that the requised condition of dӷd c for Raman analysis of GaAsN in TO symmetry generates such poor crystalline quality that the intrinsic N r rate is altered. This is ruled out below.…”

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“…Raman analysis is performed in geometries ͑1͒ and ͑2͒ with nonresonant 647.1 nm Ar ϩ excitation, which is relevant at low x. 8 The spectra in geometry ͑1͒ obtained with GaAs 1Ϫx N x are shown in Fig. 1.…”

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“…It is on this very basis that the atypical Be͑Se,Te͒-like two-mode behavior in Zn-Be chalcogenides was interpreted. 7,8 Accordingly the low-and high-frequency modes were labeled with superscripts h and s, respectively. Basically, our view is that in ͑N,Be͒-based systems, which constitute a class of semiconductor alloys made of parent materials with mechanical contrast, the short-bond frequencies are primarily determined by the mechanical properties of a͒ Author to whom correspondence should be addressed; electronic mail: pages@ipc.sciences.univ-metz.fr APPLIED PHYSICS LETTERS VOLUME 82, NUMBER 17 28 APRIL 2003 the surrounding medium, not by the local composition.…”

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“…The same holds true for the Be reference. 7,8 This establishes that the extra mode observed in geometry ͑1͒ can be safely regarded as a true LO mode with regard to the symmetry, which excludes activation by structural disorder. Incidentally this helps to decide about point ͑i͒.…”

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Percolation-based vibrational picture to estimate nonrandom N substitution in GaAsN alloys

Pagès

Tite

Bormann³

et al. 2003

Applied Physics Letters

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The number of N atoms in N-rich regions mostly due to nonrandom N incorporation in GaAsN (N∼4%), referred to as the Nr rate, is studied using a nonstandard Raman setup that addresses transverse symmetry. The Ga–N optical range shows a two-mode signal which discriminates between the N-poor (Np) and N-rich (Nr) regions. This is discussed via a percolation-based picture for Be-chalcogenide alloys, which exhibit mechanical contrast with regard to the shear modulus. This applies to GaAs–GaN even though the contrast is in the bulk modulus. The balance of Nr/Np strength provides a Nr rate of ∼30%, i.e., much larger than the corresponding Be rate of ∼4% in random Be-based alloys.

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ZnTe: phonon frequencies, mode-Grüneisen parameters

Rößler

2013

New Data and Updates for Several Semiconductors With Chalcopyrite Structure, for Several II-VI Compounds and Diluted Magnetic I

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Percolation behavior in the Raman spectra of ZnBeTe alloy

Cited by 30 publications

References 12 publications

Long-wave phonons inZnSe−BeSemixed crystals: Raman scattering and percolation model

Long-wave phonons inZnSe−BeSemixed crystals: Raman scattering and percolation model

Percolation-based vibrational picture to estimate nonrandom N substitution in GaAsN alloys

ZnTe: phonon frequencies, mode-Grüneisen parameters

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