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Impacts of surface depletion on the plasmonic properties of doped semiconductor nanocrystals

Nature Materialsvolume 17pages710717 (2018) | Download Citation


Degenerately doped semiconductor nanocrystals (NCs) exhibit a localized surface plasmon resonance (LSPR) in the infrared range of the electromagnetic spectrum. Unlike metals, semiconductor NCs offer tunable LSPR characteristics enabled by doping, or via electrochemical or photochemical charging. Tuning plasmonic properties through carrier density modulation suggests potential applications in smart optoelectronics, catalysis and sensing. Here, we elucidate fundamental aspects of LSPR modulation through dynamic carrier density tuning in Sn-doped In2O3 (Sn:In2O3) NCs. Monodisperse Sn:In2O3 NCs with various doping levels and sizes were synthesized and assembled in uniform films. NC films were then charged in an in situ electrochemical cell and the LSPR modulation spectra were monitored. Based on spectral shifts and intensity modulation of the LSPR, combined with optical modelling, it was found that often-neglected semiconductor properties, specifically band structure modification due to doping and surface states, strongly affect LSPR modulation. Fermi level pinning by surface defect states creates a surface depletion layer that alters the LSPR properties; it determines the extent of LSPR frequency modulation, diminishes the expected near-field enhancement, and strongly reduces sensitivity of the LSPR to the surroundings.

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This research was supported by the National Science Foundation (NSF, CHE-1609656) and the Welch Foundation (F-1848).

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Author notes

  1. These authors contributed equally: Omid Zandi, Ankit Agrawal


  1. McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas, USA

    • Omid Zandi
    • , Ankit Agrawal
    • , Alex B. Shearer
    • , Lauren C. Reimnitz
    • , Clayton J. Dahlman
    • , Corey M. Staller
    •  & Delia J. Milliron


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O.Z. and A.A. contributed equally to this work. O.Z. synthesized the materials, fabricated devices and performed experimental FTIR spectroscopy, A.A. performed simulations, A.S. synthesized Sn:In2O3 nanocrystals, L.G. performed analysis of TEM images, C.J.D. provided critical conceptual inputs, C.M.S. performed ICP, D.J.M. provided overall guidance, and O.Z., A.A. and D.J.M. wrote the manuscript with critical input from all the authors.

Competing interests

D.J.M. has a financial interest in Heliotrope Technologies, a company pursuing commercialization of electrochromic devices.

Corresponding author

Correspondence to Delia J. Milliron.

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    Supplementary Sections 1–10, Supplementary Figures 1–22, Supplementary Table 1, Supplementary References 1–16

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