Silicon Nanoparticles from the Inside Out: Exploring the Internal Structure of Silicon Nanoparticles and Its Impact on Their Photoluminescence

• Author / Creator

  Thiessen, Alyxandra N.

• Silicon nanoparticles (SiNPs) have garnered significant attention as a biologically compatible alternative to traditional quantum dots. SiNPs are well suited for a wide range of applications due to their photoluminescence (PL) and chemical properties. These advantageous properties can be controlled on the basis of the internal and surface structure of the SiNPs. The internal structure can be tuned during the synthesis of the SiNP core, while the surface typically is modified by functionalization after. This thesis examines the internal structure of SiNPs and the impact of the internal structure on the luminescence response.
  Chapter 1 introduces SiNPs and the important role that the structure plays on their properties. Chapter 2 explores the internal structure of 3, 6, 9, 21, and 64 nm hydride-terminated SiNPs (H-SiNPs) using a series of characterization techniques. A graded internal structure is identified, consisting of a crystalline core, a semi-ordered subsurface, and a disordered surface. This structure breaks down for 3 and 6 nm SiNPs, in which no long-range order is observed.
  The insight from Chapter 2 is used in Chapter 3 to explore the impact of the internal structure on the photoluminescence properties. Two groups of SiNPs were studied, one with a thick amorphous shell (>1 nm) and one with a thin amorphous shell (<0.8 nm), determined by the difference between the overall diameter (dTEM) and the crystalline domain size (dXRD). For SiNPs with a thick amorphous shell, the PL emission maximum (PL max) and lifetimes correlate better with dXRD than dTEM, while PL max and lifetimes correlate well with both dXRD and dTEM for SiNPs with a thin amorphous shell.
  The impact of oxidation on the internal structure of SiNPs and their photoluminescence is outlined in Chapter 4. Upon oxidation, a decrease in dXRD and an increase in dTEM are observed that appear to correlate with the SiNP size, where smaller SiNPs show a larger change in dXRD and dTEM. This corresponds with a size-dependent blue-shift in the PL max with increasing oxidation. A summary of the experimental chapters is provided in Chapter 5, along with future research directions.

• Subjects / Keywords

  • Silicon Nanoparticles
  • Quantum Dots
  • Photoluminescence
  • Silicon

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-e23c-9313

• License

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