Raman spectra of ordered vacancy compounds in the Cu-In-Se system

• Published in: Japanese Journal of Applied Physics Vol. 36; no. 8B; pp. L1075 - L1077
• Main Authors: NOMURA, S, OUCHI, S.-I, ENDO, S
• Format: Journal Article
• Language: English
• Published: Tokyo Japanese journal of applied physics 15.08.1997
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Infrared and raman spectra and scattering; Lattice dynamics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other nonmetallic inorganics; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; Copper selenides; Raman spectra; Inorganic compounds; Indium selenides; Vacancies; Ternary compounds; Transition element compounds; Lattice vibrations; Experimental study
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/jjap.36.l1075

Raman spectra of ordered vacancy compounds (OVC) of CuIn 2 Se 3.5 and CuIn 3 Se 5 have been measured at room temperature. Similar nonpolarized Raman spectra are obtained for CuIn 2 Se 3.5 and CuIn 3 Se 5 . However, polarized Raman spectra are not available for CuIn 3 Se 5 because of its unfavorable crystallinity. A signal at 154  cm -1 is assigned to be Γ 1 mode of D 2 d symmetry, originating from the vibration of selenium atoms in the x - y ( a -axes) plane. This signal corresponds to the signal at 178  cm -1 for CuInSe 2 of chalcopyrite-type in the Cu-In-Se system. The lowering of Γ 1 mode frequency for the defect structure is attributed to looser-bound selenium atoms on account of vacancies in the cation sites. Signals assigned as Γ 3 mode are unexpectedly observed in the geometries allowing the longitudinal optical (LO) modes of Γ 4 and Γ 5 symmetries. The respective mode peaks are found to be more dispersive in frequency for CuIn 2 Se 3.5 than for CuInSe 2 .