Ultrafast Photoluminescence in Quantum-Confined Silicon Nanocrystals Arises from an Amorphous Surface Layer

Daniel C. Hannah, Jihua Yang, Nicolaas J. Kramer, George C. Schatz, Uwe R. Kortshagen, Richard D. Schaller

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Here, we examine ultrafast photoluminescence produced from plasma-grown, colloidal silicon nanocrystals as a function of both particle size and lattice crystallinity. In particular, we quantify the decay time and spectral profiles of nominally few-picosecond direct-gap emission previously attributed to phononless electron-hole recombination. We find that the high-energy (400-600 nm, 2-3 eV) photoluminescence component consists of two decay processes with distinct time scales. The fastest photoluminescence exhibits an ∼30 ps decay constant largely independent of emission energy and particle size. Importantly, nearly identical temporal components and blue spectral features appear for amorphous particles. We thus associate high-energy, rapid emission with an amorphous component in all measured samples, as supported by Raman analysis and molecular dynamics simulation. Based on these observations, we advise that the observed dynamics proceed too slowly to originate from intraband carrier thermalization and instead suggest a nonradiative origin associated with the amorphous component.

Original languageEnglish
Pages (from-to)960-967
Number of pages8
JournalACS Photonics
Volume1
Issue number10
DOIs
Publication statusPublished - Oct 15 2014

Keywords

  • amorphous silicon
  • nanocrystal
  • photoluminescence
  • quantum dot
  • silicon
  • spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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