Observations of surface and projected bulk phonons in epitaxial overlayers: the Cu(100) and Cu(100)/Co system

Abstract

The phonon spectra of both clean and cobalt covered Cu(100) have been studied with helium atom scattering, and the results compared with those previously obtained with EELS for nickel and iron overlayers on Cu(100) [1,2]. In the Γ-M direction on clean Cu(100), both Rayleigh and bulk band edge phonons were observed. In the Γ-X direction, surface Rayleigh modes with dispersion similar to that obtained in EELS [3] occurred together with a previously unobserved, higher energy mode. No change in phonon dispersion was found for cobalt covered Cu(100).