Laterally tunable plasmon resonance in confined biatomic-layer ag nanodisks.

We report on the fabrication and investigation of the plasmon excitations in laterally confined quasi-two-dimensional (2D) Ag nanodisks on a Si(111) substrate. Different from the Mie resonance in Ag clusters and the propagating plasmon waves in 2D systems, these ultrathin nanodisks exhibit a low-energy plasmon resonance whose frequency is continuously tunable by the disk diameter. Quantum-mechanical simulations revealed the origin and the effects of screening and charge transfer on the plasmon excitation. The character and size-dependence are promising for engineering plasmonic and optical properties in supported 2D systems.