The Elastic and Structural Properties of Copper - Superlattices

A series of Cu-Pd superlattices with wavelength (lambda) varying from 1.2 to 3.5 nm have been prepared in a UHV evaporator. The films have been characterized using x-ray diffraction and high resolution electron microscopy. The elastic properties of the films have been studied using the uniaxial tension test, Brillouin scattering and variable length acoustic wave measurements to measure the flexural, shear and Young's modulus of the films. The Cu-Pd system has previously been studied, and conflicting reports have been present as to the appearance of the supermodulus effect. The films have been seen to be structurally similar to films in which the supermodulus effect has previously been observed. The value of the amplitude of the composition modulation is roughly equal to the value found in past studies. The HREM study has shown that the films are structurally similar to films in which the supermodulus effect has previously been observed. The elastic property measurements all show that the films have moduli which are roughly equal to, or slightly less than the value predicted classically for a Cu-Pd superlattice based on the elastic constants of Cu and Pd. No evidence for the supermodulus effect has been detected in the films that were prepared in the present study.