Role of adsorption site on electron-energy-loss cross sections of single-layer substrate modes

Abstract

We show that shear horizontal modes Sl and S5 may have measurable inelastic electron scattering cross sections if a c(2&2) overlayer is adsorbed on a (001) surface. The nonzero cross sections arise from preferential shadowing of substrate atoms by the overlayer. Whether Sl or S5 has nonzero cross section is an indicator of the adsorption site. Also, the number of nonzerocross-section Rayleigh (S4) modes depends on the adsorption site.