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 Ed measured by means of the vibrating reed method with the strain amplitude εt=10-6 is found to be lower than Es in the frequency f range below (103~104) Hz, showing a minimum at around 102 Hz, and to increase beyond Es in the f range above (103~104) Hz, where Es 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 εt dependence of Ed measured at f=102Hz shows that Ed increases towards Es with increasing εt. Further, for the measurements at f=102Hz with t=10-6, an increase in Ed 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.