The influence of conjugated alkynyl(aryl) surface groups on the optical properties of silicon nanocrystals: Photoluminescence through in-gap states

Arzu Angi, Regina Sinelnikov, Hendrik H. Heenen, Al Meldrum, Jonathan G.C. Veinot, Christoph Scheurer, Karsten Reuter, Or Ashkenazy, Doron Azulay, Isaac Balberg, Oded Millo*, Bernhard Rieger

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Developing new methods, other than size and shape, for controlling the optoelectronic properties of semiconductor nanocrystals is a highly desired target. Here we demonstrate that the photoluminescence (PL) of silicon nanocrystals (SiNCs) can be tuned in the range 685-800 nm solely via surface functionalization with alkynyl(aryl) (phenylacetylene, 2-ethynylnaphthalene, 2-ethynyl-5-hexylthiophene) surface groups. Scanning tunneling microscopy/spectroscopy on single nanocrystals revealed the formation of new in-gap states adjacent to the conduction band edge of the functionalized SiNCs. PL red-shifts were attributed to emission through these in-gap states, which reduce the effective band gap for the electron-hole recombination process. The observed in-gap states can be associated with new interface states formed via (-Si-C≡C-) bonds in combination with conjugated molecules as indicated by ab initio calculations. In contrast to alkynyl(aryl)s, the formation of in-gap states and shifts in PL maximum of the SiNCs were not observed with aryl (phenyl, naphthalene, 2-hexylthiophene) and alkynyl (1-dodecyne) surface groups. These outcomes show that surface functionalization with alkynyl(aryl) molecules is a valuable tool to control the electronic structure and optical properties of SiNCs via tuneable interface states, which may enhance the performance of SiNCs in semiconductor devices.

Original languageAmerican English
Article number355705
JournalNanotechnology
Volume29
Issue number35
DOIs
StatePublished - 25 Jun 2018

Bibliographical note

Publisher Copyright:
© 2018 IOP Publishing Ltd.

Keywords

  • conjugated surface groups
  • in-gap states
  • photoluminescence
  • quantum dots
  • scanning tunneling microscopy/spectroscopy
  • silicon nanocrystals
  • surface functionalization

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