Ultrasonic Properties of Pure and Ag-Doped Amorphous Chalcogenides (As2S3, As2Se3)

Abstract

The lattice (elastic and relaxation) properties of the amorphous chalcogenides, mainly on pure and Ag-doped As 2 S 3 , have been studied by measuring ultrasonic velocities and attenuations. The observed drastic increase (5∼10%) of the velocity with a small amount (1 at.%) of doped Ag in As 2 S 3 has been attributed to its anomalous behaviors of the density, the anharmonicity and the bulk modulus due to the doping. The experimental temperature dependences of shear wave attenuation α s ( T ) and of high-frequency electrical conductivity σ( T ) in As 2 S 3 are both well represented by exp (- E h / k t ) with approximately the same activation energy E h ∼0.1 eV. The mechanism of the phonon-assisted hopping of As–S dipoles (activated by thermal phonons) has been shown to explain the identical temperature dependence for α s ( T ) and σ( T ). Thus, these are the two manifestations, the mechanical relaxation (α) and the dielectric relaxation (σ), of the same origin, i.e., due to the hopping of ions, perhaps mainl...