Optical phonons in AgGaSe₂

Abstract

Abstract Polarised infrared reflectivity measurements are made on a single crystal of the chalcopyrite compound, AgGaSe 2 . This is the only selenium I—III—VI 2 compound so far investigated for zone centre phonon properties. They are compared with previous studies of lattice dynamics in the sulphide family and its binary zinc blende analogues. Four modes having E irreducible representation are observed between 35 and 75 μm with the light polarised perpendicular to the c ‐axis, while two B 2 modes are observed in the range 35 to 65 μm with the light polarised parallel to the c ‐axis. A classical dispersion harmonic oscillator computer fit is made to the data to give the oscillator parameters.