  Nanoplasmonics exploits the coupling between light and collective electron
density oscillations (plasmons) to bypass the stringent limits imposed by
diffraction. This coupling enables confinement of light to sub-wavelength
volumes and is usually exploited in nanostructured metals. Substantial efforts
are being made at the current frontier of the field to employ electron systems
in semiconducting and semimetallic materials since these add the exciting
possibility of realizing electrically tunable and/or active nanoplasmonic
devices. Here we demonstrate that a suitable design of the doping profile in a
semiconductor nanowire (NW) can be used to tailor the plasmonic response and
induce localization effects akin to those observed in metal nanoparticles.
Moreover, by field-effect carrier modulation, we demonstrate that these
localized plasmon resonances can be spatially displaced along the nanostructure
body, thereby paving the way for the implementation of spatially tunable
plasmonic circuits.

Mesoscale and Nanoscale Physics