Angle-resolved photoemission study of quantized electronic structures on Ag nanofilms

We carried out an angle-resolved photoemission study on Ag nanofilms of various thicknesses in order to investigate the quantized electronic structure. In the valence band photoemission spectra, we found the additional fine-structures originated from the quantized electronic states due to the confinement of electrons within the Ag nanofilms. The spectral binding energy dependence on Ag nanofilm thickness is well characterized by the phase accumulation model which takes into account the phase shifts on the reflections at both interfaces of Ag nanofilms. From detailed angle-resolved photoemission measurements, the two-dimensional dispersion relations for these quantized electronic states were determined. It is also found that these quantized electronic states can be observed within the projected band structure mismatch region to the surface Brillouin zone of Ag(111) and Cu(111). This indicates that the confinement of electrons on the present system occurs rigidly due to the band structure mismatch between Ag and Cu.