Elastic and Anelastic Properties of Amorphous Thin Films

Abstract
The interesting non-linear elastic and anelastic properties recently found in the metal-metal and the metal-metalloid amorphous alloys will be reported. The Young's modulus E_d measured by means of the vibrating reed method with the strain amplitude ε_t=10^-6 is found to be lower than E_s in the frequency f range below (10³~10⁴) Hz, showing a minimum at around 10² Hz, and to increase beyond E_s in the f range above (10³~10⁴) Hz, where E_s denotes the Young's modulus in linear elasticity observed for the static tensile or bending tests. These results suggest that a certain resonant anelastic-process is excited under alternating strain in the f range below (10³~10⁴) Hz. The ε_t dependence of E_d measured at f=10²Hz shows that E_d increases towards E_s with increasing ε_t. Further, for the measurements at f=10²Hz with _t=10^-6, an increase in E_d is also found but under passing an electric direct current (PEC) with 10⁷A/m², suggesting that internal stress is induced under PEC. These results suggest the view that a certain cluster of many atoms undergoes a resonant motion under alternating strain, and also yields internal stress due to the concentration of the electromigration force through a collective motion under PEC. The effective charge number Z* which measures internal stress induced under PEC is found to be the order of 10⁵ for all the amorphous alloys. The number of atoms involved in the above cluster is estimated to lie between 10² and 10⁵.