Temperature dependence of photoemission from quantum-well states in Ag/V(100):  Moving surface-vacuum barrier effects

The temperature dependence of angle-resolved photoemission from quantum-well states in ultrathin films of Ag on V(100) has been examined for films from 1–8 ML thickness within the temperature range 45–600 K. Contrary to bulk solids, the photoemission peaks shift to higher binding energy as the temperature is increased. The temperature dependence of the peak widths is linear, consistent with the expected behavior for electron-phonon coupling, but the coupling parameter λ is found to show a strong oscillatory dependence on film thickness, with some values many times larger than those found for bulk silver. The observations are explained in terms of the influence on both the initial and final states in the photoemission process of the static and dynamic movements of the surface-vacuum interface barrier induced by temperature changes.