Proceedings of September Meeting 2016 (NFM16)
Publication date: 14th June 2016
Degenerately doped metal oxide semiconductors exhibit plasmonic resonance at near and mid-infrared wavelengths tunable by varying their composition. Nanocrystals of many such materials have now been synthesized and applications are emerging that leverage the responsiveness of their localized surface plasmon resonance (LSPR) to electronic charging and discharging. We are developing methods to tune their LSPR spectra and thereby design plasmonic oxide nanocrystals deliberately for different applications, ranging from localized photothermal heating to enhanced spectroscopies for molecular detection. Such applications depend on the nature of the plasmonic modes and the damping of plasmonic excitations, characteristics which are also reflected in LSPR line shapes. For example, to maximize the potential for near-field enhancement, we must minimize electronic scattering. Our results indicate that engineering the dopant distribution within the nanocrystals and selecting dopants to minimize electronic hybridization with the conduction band are two effective strategies to this end, resulting in dramatically reduced LSPR linewidths. Tuning anisotropy of metal oxide nanocrystals offers another route to engineer their plasmonic modes, thereby tuning the spatial distribution and intensity of near-field hot spots surrounding the nanocrystals. We show that in semiconducting metal oxides, both shape and the underlying crystalline anisotropy collaborate to produce tunable multi-modal LSPR properties.