Nonequilibrium-Plasma-Synthesized ZnO Nanocrystals with Plasmon Resonance Tunable via Al Doping and Quantum Confinement

Benjamin L. Greenberg, Shreyashi Ganguly, Jacob T. Held, Nicolaas J. Kramer, K. Andre Mkhoyan, Eray S. Aydil, Uwe R. Kortshagen

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Metal oxide semiconductor nanocrystals (NCs) exhibit localized surface plasmon resonances (LSPRs) tunable within the infrared (IR) region of the electromagnetic spectrum by vacancy or impurity doping. Although a variety of these NCs have been produced using colloidal synthesis methods, incorporation and activation of dopants in the liquid phase has often been challenging. Herein, using Al-doped ZnO (AZO) NCs as an example, we demonstrate the potential of nonthermal plasma synthesis as an alternative strategy for the production of doped metal oxide NCs. Exploiting unique, thoroughly nonequilibrium synthesis conditions, we obtain NCs in which dopants are not segregated to the NC surfaces and local doping levels are high near the NC centers. Thus, we achieve overall doping levels as high as 2 × 1020 cm-3 in NCs with diameters ranging from 12.6 to 3.6 nm, and for the first time experimentally demonstrate a clear quantum confinement blue shift of the LSPR energy in vacancy- and impurity-doped semiconductor NCs. We propose that doping of central cores and heavy doping of small NCs are achievable via nonthermal plasma synthesis, because chemical potential differences between dopant and host atoms - which hinder dopant incorporation in colloidal synthesis - are irrelevant when NC nucleation and growth proceed via irreversible interactions among highly reactive gas-phase ions and radicals and ligand-free NC surfaces. We explore how the distinctive nucleation and growth kinetics occurring in the plasma influences dopant distribution and activation, defect structure, and impurity phase formation.

Original languageEnglish (US)
Pages (from-to)8162-8169
Number of pages8
JournalNano letters
Volume15
Issue number12
DOIs
StatePublished - Dec 9 2015

Keywords

  • aluminum-doped zinc oxide
  • doping
  • nanocrystals
  • plasma
  • plasmonics
  • quantum confinement

How much support was provided by MRSEC?

  • Primary

Reporting period for MRSEC

  • Period 2

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

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