title: Plasmon response of a quantum-confined electron gas probed by core-level photoemission.
abstract: We demonstrate the existence of quantized "bulk" plasmons in ultrathin magnesium films on Si(111) by analyzing plasmon-loss satellites in core-level photoemission spectra, recorded as a function of the film thickness d. Remarkably, the plasmon energy is shown to vary as 1/d2 all the way down to three atomic layers. The loss spectra are dominated by the n=1 and n=2 normal modes, consistent with the excitation of plasmons involving quantized electronic subbands. With decreasing film thickness, spectral weight is gradually transferred from the plasmon modes to the low-energy single-particle excitations. These results represent striking manifestations of the role of quantum confinement on plasmon resonances in precisely controlled nanostructures.
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Mustafa M
authors.initials: MM
authors.lastname: Özer
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Moon
authors.forename: Adolfo G
authors.initials: AG
authors.lastname: Eguiluz
authors.forename: Hanno H
authors.initials: HH
authors.lastname: Weitering