Ultrafast Photoluminescence Spectroscopy of Silicon Nanocrystals

• Author / Creator

  De los Reyes, Glenda B

• Ultrafast carrier dynamics in silicon nanocrystals (Si NCs) is explored using time-integrated photoluminescence, time-resolved photoluminescence and pump-probe transient absorption spectroscopies.
  The role of surface oxygen in the optical emission dynamics of dodecyl functionalized Si NCs is explored. Significant surface oxidation results in a photoluminescence blue shift and an observation of sub-10 ns recombination lifetime. In addition, surface oxidation improves the absolute quantum yield of dodecyl functionalized Si NCs. This study also shows that surface passivation plays an important role in the emission dynamics of functionalized Si NCs. It is shown that photoluminescence in silicon nanocrystals can be tuned by changing the surface passivation alone. Tunable surface-related emissions are significantly blue shifted compared to quantum confinement predictions and exhibit a faster recombination rate similar to that for direct bandgap semiconductors. Furthermore, the photoluminescence quantum yields of these silicon nanocrystals are higher than those that exhibit quantum core state emission. On the other hand, detailed time-resolved photoluminescence studies reveal that the origin of the size-independent blue emission in dodecylamine and ammonia functionalized Si NCs originates from charge transfer states located at the silicon-silicon oxynitride interface. Time-integrated photoluminescence spectroscopy revealed that Si NCs with silicon volume filling fraction below the percolation threshold exhibit strong size-dependent emission in the infrared region. The carrier dynamics of these Si NCs are explored using pump-probe transient absorption spectroscopy with sub-picosecond resolution and time-resolved photoluminescence spectroscopy in
  the nanosecond and microsecond time scales. Si NC films exhibit sub-picosecond, sub-nanosecond and microsecond lifetimes attributed to carrier trapping at the oxygen-related defects, carrier recombination at the trap states and carrier recombination via the silicon core state, respectively. The results of this study will hopefully contribute to the understanding of the role of oxygen in the optical emission properties of functionalized Si NCs. In addition, the blue emission observed in dodecylamine and ammonia functionalized Si NCs will impact applications in optoelectronic devices. Finally, 800 nm, 65 fs laser pulses is coupled to near-field scanning optical microscopy using single mode fiber. The newly developed ultrafast NSOM is suitable for studying spatially-resolved PL emission in semiconductor nanostructures.

• Subjects / Keywords

  • Time correlated single photon counting
  • Blue-emitting silicon nanocrystals
  • Silicon nanocrystals
  • Ultrafast near-field scanning optical microscopy
  • Oxygen-related defects
  • Time-resolved photoluminescence
  • Charge transfer state
  • Photoluminescence
  • Charge transfer state emission
  • Silicon nanocrystal films

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R37M04B1V

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.