Enhancing Plasmon Quality Factor for Photonic Materials via Solvothermal Annealing in Cd ₂ SnO ₄ Nanocrystals

Photonic properties in a plasmonic nanocrystal are directly impacted by carrier density, carrier effective mass, and carrier damping behavior. Postprocessing of as-prepared Cd 2 SnO 4 (CTO) by solvothermal annealing is shown to enhance the localized surface plasmon (LSPR) optical quality through a time-dependent LSPR shift and LSPR narrowing. The change in the LSPR is complex but postulated to be driven by surface reconstruction leading to incorporation of Sn, reduction in size, and defect evolution. The changes in the CTO produce a shift to higher frequency for the LSPR and loss of a high energy shoulder with an exponential rate of k ∼ 1.0 h –1 . The improved plasmonic quality factor is due to the overall increase in carrier density and loss of the shoulder during solvothermal annealing. During annealing, an increase in the depletion layer width and a decrease in Sn activation in CTO with k ∼ 0.5 h –1 are also observed. Postprocessing of isolated plasmonic metal oxide nanocrystals through solvo-thermal annealing may represent a convenient strategy to enhance LSPR quality factors, providing a pathway to improving photonic properties in this class of materials.