2014 年 35 巻 8 号 p. 409-414
Photoemission spectroscopy is one of the most reliable and versatile experimental techniques in the field of surface science. The recent improvement of the energy resolution enables us to observe the inelastic scattering process induced by the electron-phonon interaction during laser photoemission process. One example is the appearance of step structures in the laser photoemission spectra（LPES） in addition to the elastic component fitted by Fermi-Dirac distribution. In this article, we investigate the origin of this step structure in the Cu(110) spectra by using ab-initio density functional and density functional perturbation theory. We have found that the subsurface phonon modes scatter the excited electron from Y point to the Γ point around the vacuum level, which leads to this step structure. In addition to clean Cu(110), we also carried out similar analysis on the Cu(110)-(2×1)-O surface. Although the inelastic step structures appeared at the identical position within the experimental uncertainty in the Cu(110) and Cu(110)-(2×1)-O spectra, we found that the phonon modes that corresponds to the inelastic process are different in these two surfaces.
