Lattice dynamics of AgGaSe2. I. Experiment

J. Camassel, L. Artus, and J. Pascual
Phys. Rev. B 41, 5717 – Published 15 March 1990
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Abstract

We report a detailed investigation of the infrared and Raman activity of AgGaSe2. Performing, first, infrared studies in the spectral range 15–500 cm1, both at room and at liquid-helium temperature, we could identify all Γ4 (EC ) and Γ5 (EC ) vibrational modes predicted by group-theory arguments. This includes, at low energy, the complete series of folded-acoustic components resolved for the first time and second, at higher energy, a nearly degenerate Γ5 doublet at 249.5–252.1 cm1. All frequencies obtained in that way were independently checked by performing, under nearly resonant conditions, Raman investigations at 77 K. We could then identify four additional modes: 1Γ1 and 3Γ3. Our experimental results demonstrate that all zone-center modes can be grouped in three energy bands: First, within a very narrow energy range centered around 250 cm1 are four modes (1Γ3+1Γ4+2Γ5); next, in an intermediate region extending from 180 to 135 cm1 are five modes (1Γ1+1Γ3+1Γ4+2Γ5); and, finally, at much lower energy the dispersion of the acoustic branches gives, in the range 25–85 cm1, another series of four modes which are associated with 1Γ3+1Γ4+2Γ5 symmetry.

  • Received 16 August 1989

DOI:https://doi.org/10.1103/PhysRevB.41.5717

©1990 American Physical Society

Authors & Affiliations

J. Camassel

  • Groupe d’Etude des Semiconducteurs, Université des Sciences et Techniques du Languedoc, 34095 Montpellier CEDEX, France

L. Artus

  • Institut de Ciència de Materials de Barcelona (ICMAB), Consell Superior d’Investigacions Cientifiques (CSIC), calle/Marti i Franquès, 08028 Barcelona, Spain

J. Pascual

  • Departament Fisica i Institut de Ciència de Materials de Barcelona (ICMAB), Consell Superior d’Investigacions Cientifiques (CSIC), Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

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Vol. 41, Iss. 9 — 15 March 1990

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