(637b) Active Plasmonics Based Devices Using Metal Oxide Nanocrystals: Fundamental and Applications

Degenerately doped semiconductor nanocrystals (NC) exhibit a localized surface plasmon resonance (LSPR) that falls in the near- to mid-IR range of the electromagnetic spectrum. Unlike metal LSPR, the metal oxide LSPR can be tuned by doping, and structural control, or by in situ electrochemical or photochemical charging. While synthetic work to demonstrate active plasmonic using this class of materials has progressed significantly, quantitative correlation between their intrinsic properties to the final LSPR tunability properties enhancement remains poorly explored, thus prohibiting their optimal use in wide range of applications from plasmon derived smart windows to sensors. Here, we illustrate how intrinsic NC attributes like its band structure and surface properties affects the LSPR tunability properties and its possible applications.

Here in this work, LSPR modulation through dynamic carrier density tuning was investigated using thin films of monodisperse ITO NCs with various doping level and sizes along with an in situ electrochemical setup. From the combination of the in-situ spectroelectrochemical analysis and optical modeling, it was found that often-neglected semiconductor properties such as band structure modification upon doping and surface chemistry strongly affect the LSPR modulation behavior. The influence of band structure and effects like Fermi level pinning by surface defect states were shown to cause a surface depletion layer that alters the LSPR properties, namely the extent of LSPR modulation, near field enhancement, and sensitivity of the LSPR to the surrounding (1-3).

Reference:

1) Ankit Agrawal,Ilka Kriegel, Evan Runnerstrom, Francesco Scotognella, Anna Llordes, Delia Milliron. Rationalizing the impact of surface depletion on electrochemical modulation of plasmon resonance absorption in metal oxide nanocrystals. ACS Photonics, Article ASAP

2) Ankit Agrawal, Shin Hum Cho, Omid Zandi, Sandeep Ghosh, Robert Johns, and Delia Milliron. Localised Surface Plasmon Resonance in semiconductor nanocrystals. Chem. Rev., 118 (6), 2018, 3121–3207

3) Omid Zandi, Ankit Agrawal, Alex Shearer, Clayton Dahlman, Delia Milliron. Effect of band gap alignment and surface potential on plasmonic property of metal oxide Nanocrystals. arXiv:1709.07136