Optical and acoustical phonon properties of BeTe

Abstract We present an investigation of the vibrational properties, the elastic constant c 11 and the infrared dielectric constant e ∞ of BeTe. For this purpose we applied far-infrared reflectance and Raman spectroscopy to single BeTe layers and BeTe/ZnSe superlattices. The experimental data are used to access the bond ionicity in the framework of an empirical tight binding approach. A low bond polarity of 0.61 is determined for BeTe, which corresponds to a high lattice stability. Furthermore, the elastic constant c 11 is determined as to be 8.9 ± 0.9.10 10 N/m 2 from the frequency positions of folded acoustic phonon (FAP) modes in BeTe/ZnSe superlattices. The experimental results are correlated to data obtained by first-principles local density approximation (LDA) calculations.