The influence of copper and iodine impurities on the velocity and attenuation of ultrasound in amorphous As2Se3

Abstract

The velocity and attenuation of longitudinal acoustic waves in the frequency range 10–100 MHz has been measured in amorphous arsenic selenide, pure and with copper and iodine doping. Both kinds of impurities cause an increase of attenuation but they have different influences on the velocity of acoustic waves. While the velocity increases with increasing concentration of Cu, doping with I causes a decrease of the acoustic wave velocity. Particular attention has been given to the frequency and temperature dependence of attenuation in pure and doped samples, which show behaviour quite different from that in dielectric crystals. Two scattering mechanisms have been proposed for the interpretation of the attenuation in pure samples. One is scattering due to the static strain field and the anharmonicity of the interatomic forces, and the other is due to the interaction with the thermal phonons. In doped samples impurities are responsible for an additional attenuation.