LATTICE REFLECTION AND OPTICAL CONSTANTS OF ZNSNP2 CRYSTALS WITH CHALCOPYRITE AND SPHALERITE STRUCTURE

The infra‐red reflectivity of ZnSnP2 has been investigated in the wavelength range 2 to 60μm at T = 295 °K. The optical constants and vibrational frequencies are determined; for the chalcopyrite structure they are ϵ∞ = 8.1 ± 0.2, ϵ0 = 10.0 ± 0.4, n = 2.84 ± 0.04, ωl 0 = 368 cm−1, ωt 0 = 330 cm−1; for the sphalerite structure they are ϵ∞ = 8.3 ± 0.2, ϵ0 = 10.8 ± 0.4, n = 2.88 ± 0.04, ωl 0 = 362 cm−1, ωt 0 = 318 cm−1. The effective ionic charge is estimated by the Szigeti formula. The values are for the chalcopyrite structure e*/e = 0.58, for the sphalerite structure e*/e = 0.63. The compressibility has been estimated to β × 1012 = 1.28 and 1.34 (cgs units) for the chalcopyrite and sphalerite structure, respectively, and the Blackman sum rule has been checked. The parameters of the dispersion oscillators have been obtained from dispersion analysis. The magnitude of the parameter γ characterizing the damping of the oscillator, γ = 0.061 (chalcopyrite structure) and γ = 0.110 (the sphalerite structure), exceeds the corresponding values for the compound GaP and InP; that is possibly due to stronger phonon‐phonon interaction in ZnSnP2. Using dispersion analysis and Kramers‐Kronig analysis the disperison of the refractive index and the dielectric constant due to the lattice vibrations has been calculated. Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim