Cross-section analysis of surface and bulk phonons by electron scattering from Cu(100)

High-resolution electron energy-loss measurements at off-specular directions on a clean Cu(100) surface ($\overline{\Gamma }-\overline{X}$ direction) demonstrate the presence of both surface and bulk phonon excitations. We present what we believe to be the first detailed cross-section analysis of surface and bulk phonon excitations on the Cu(100) surface. The data are shown to be in very good agreement with calculations based on the multiple-scattering slab method. The achievement of experimental phonon intensities one to two orders of magnitude higher than previously obtained is also demonstrated.