| This thesis presents photoemission studies of electron behaviors on stepped metal surfaces, utilizing laser pulses as the probing tools. Electrons are excited to the image states, ionized by laser beams and detected as a function of geometric configurations, energetic distributions and temporal evolutions. Specifically, two-photon photoemission (2PPE) techniques are used to investigate the influences of steps on image-state electrons, such as the change of energetics and dynamics.;Angle-resolved two-photon photoemission studies of surface-state electrons on single-crystal stepped Cu(001) and Cu(111) surfaces are first demonstrated. Lateral superlattice effects are observed for the n = 1 image state on both surfaces. A comparative study of the dispersion of surface electrons in both crystal- and image-induced states on a stepped Cu(775) surface and the relevant flat Cu(111) surface is then presented. Because these states exist at different average distances with respect to the surface plane, they respond differently to the steps and display different dispersion behaviors.;The lifetimes of the n = 1 image electrons on flat Cu(111) surface and a regular step array on Cu(775) surface have been measured with a femtosecond optical pump-probe technique, as a function of momentum parallel to the surface. The electron lifetime is symmetric about k// = 0 when measured on flat Cu(111) and parallel to the step orientation on Cu(775), but asymmetric in the direction perpendicular to the step edges on the stepped surface. This behavior is attributed to k//-dependent coupling between image and bulk states.;Femtosecond laser provides not only time-resolved capabilities, but also a much better signal-to-noise ratio in energy spectroscopy. This has enabled observations of a one-dimensional surface state (0.27 eV below Fermi level) and an image-like unoccupied state on a stepped Cu(111) surface. Both states are dispersive along the step direction but localized perpendicular to the step orientation.;Finally, preliminary works on Si(111)7x7 and Au reconstructed Si surfaces are described. |
