Raman study of ZnxBe1−xSe alloy (100) epitaxial layers

Pagès, O.; Ajjoun, M.; Laurenti, J.P.; Bormann, D.; Chauvet, C.; Tournié, E.; Faurie, J. P.

doi:10.1063/1.127030

Cited by 27 publications

(12 citation statements)

References 13 publications

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“…We consider now the zone-center (q % 0) signal. Most of the Raman spectra available in the literature refer to the LO symmetry, and are similar to that reported in the [4,7]. However, there is clear evidence of the extra mode, shown as LO a Be-Se .…”

Section: Resultssupporting

confidence: 78%

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Vibrational Evidence for Percolative Behavior in ZnBeSe

Pagès

Ajjoun

Laurenti

et al. 2002

phys. stat. sol. (b)

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We propose a picture based on simple percolative concepts for the basic understanding of vibrational properties in the new attractive class of ternary semiconductor alloys made of materials with highly contrasted bond stiffness. In Zn 1--x Be x Se this accounts for the activation of a strong extra BeSe-like optical mode for x between the percolation thresholds of the Be-Se and Zn-Se bonds. Latter mode is attributed to Be-Se bonds within the quasi-continuous Be-rich hard-like cluster which forms above the percolation threshold.Introduction Atomic substitution in alloys A 1--x B x C brings major topological changes at the percolation thresholds of A-C and B-C bonds. These are the critical compositions associated with the first formation of pseudo-continuous wall-to-wall chains of the corresponding bonds, and were identified at x = x B-C % 0.19 and x = x A-C % 0.81 in zinc-blende systems [1]. In usual alloys these major changes do not go with anomalies for the current physical properties because parent materials are chosen similar in nature. Recently the attention turned towards the new attractive class of ternary alloys made from binaries with highly contrasted mechanical properties, and deviations from this simple picture were predicted [1]. Latter class of alloys opens the way for the observation of percolative effects by vibrational spectroscopies since these techniques address directly the force constant of the bonding, which is extremely sensitive to the mechanical properties of the host matrix.Mixed crystal ZnSe-BeSe is such a contrasted system. Vé rié [2] has predicted a highly covalent bonding for BeSe, corresponding to a small lattice parameter of 5.037 A and a high reduced shear modulus C * s of 0.478. The values for ZnSe are 5.669 A and 0.277 [3]. The longitudinal optical (LO) and transverse optical (TO) phonons of Zn 1--x Be x Se were identified by infrared and Raman analysis [4][5][6][7]. Most of Raman spectra were recorded with the 'LO-allowed/TO-forbidden' geometry. At first sight the alloy shows an MREI (modified random-element isodisplacement)-like [8] twomode behavior. This is observed in similarly mismatched alloys ZnS-ZnTe [9] and InAs-GaAs [10]. However, out of the dilute limits ZnBeSe shows an extra mode between the MREI ones [5,6]. This attracted little attention, probably because it is weak and overdamped. It does not result from structural disorder since high quality is evidenced at any x by X-ray diffraction, nor from symmetry breaking due to lattice distortion [11] since it obeys the selection rules [6]. It is an intrinsic feature since it

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Section: Resultssupporting

confidence: 78%

“…The values for ZnSe are 5.669 A and 0.277 [3]. The longitudinal optical (LO) and transverse optical (TO) phonons of Zn 1--x Be x Se were identified by infrared and Raman analysis [4][5][6][7]. Most of Raman spectra were recorded with the 'LO-allowed/TO-forbidden' geometry.…”

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confidence: 99%

Vibrational Evidence for Percolative Behavior in ZnBeSe

Pagès

Ajjoun

Laurenti

et al. 2002

phys. stat. sol. (b)

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“…4,5,14,15 Most of the attention was awarded to the long-wave transverse-optical (TO) modes, because these consist of quasi-independent oscillators, and thereby carry clear information. Complexity arises in the longitudinal-optical (LO) symmetry, due to coupling via the macroscopic polarization field.…”

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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“…Zn 1-x Be x Se semiconductors show a typical two-mode behavior at all temperatures for investigated beryllium content. It is known from the literature [17][18][19] that for high Be content (x > 0.60) in Zn 1-x Be x Se mixed crystals extra modes between the MREI ones appear in the Raman spectra. The frequencies of the vibrational modes in Zn 1-x Be x Se at RT and LNT as a function of beryllium content were determined using the parameters listed in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Raman scattering study of ZnBeSe semiconducting mixed crystals

Szybowicz¹,

Kozielski

Firszt

et al. 2003

Cryst. Res. Technol.

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The results of a study of Raman scattering of Zn 1-x Be x Se mixed crystals are reported. Raman measurements were performed for crystals with x = 0.12 and x = 0.25 Be at room temperature and liquid nitrogen temperature. From the Raman spectra the longitudinal optical and transverse optical modes which correspond to ZnSe-like and BeSe-like were distinguished. Theoretical calculations of frequencies of BeSe modes and force constants for Zn 1-x Be x Se were also performed using modified random element isodisplacement model. It has been shown that the dependence of the phonon energy on temperature may be described by the modified Klemens model.

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Raman study of ZnxBe1−xSe alloy (100) epitaxial layers

Cited by 27 publications

References 13 publications

Vibrational Evidence for Percolative Behavior in ZnBeSe

Vibrational Evidence for Percolative Behavior in ZnBeSe

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

Raman scattering study of ZnBeSe semiconducting mixed crystals

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