Tailoring the Material Properties of Doped Silicon Nanoparticles

• Author / Creator

  Milliken, Sarah C.

• Silicon nanoparticles have sparked researchers’ interest as a biologically compatible and abundant quantum dot alternative. Doped silicon nanoparticles (SiNPs) offer unique optical and electronic properties that are not observed for intrinsic Si. These advantageous properties can be applied towards a number of exciting applications such as medical imaging, photovoltaic devices, lighting, and catalysis. In order to fully realize the potential of doped SiNPs it is necessary to precisely control the particle size and surface chemistry, as well as the dopant concentration and distribution within the NP. This thesis focuses on developing synthetic methods to create well-defined and tailorable doped SiNPs.
  In Chapter 2 we aim to derivatize the surfaces of doped SiNPs obtained from the thermal processing of HSQ and boric acid. Surface modification of these SiNPs was achieved using a phosphorous pentachloride etching induced reaction with alkoxy ligands of varied chain lengths. Throughout this investigation we assessed the SiNP surface chemistry of as-synthesized B-doped SiNPs through a combination of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy (CP MAS NMR). The successful attachment of the alkoxy ligands to the surface of the particle is then assessed by FTIR, XPS and thermogravimetric analysis (TGA) and the change in photoluminescence emission is observed.
  With a convenient method for tailoring the surface chemistry of B-doped SiNPs in hand, we turned our attention toward achieving size-controlled preparation of doped particles. This saw the development of a new diffusion-based post-synthesis doping method that drew inspiration from thermally induced diffusion doping of bulk silicon. Chapter 3 describes a thermal diffusion-based post-synthesis doping method that exploits parent SiNPs with narrow size distributions, boric acid as the dopant source and hydrogen silsesquioxane as a capping agent. The role of annealing atmosphere and structural disorder within the SiNPs were found to strongly influence doping through characterization with TGA, XPS and TGA. The method allows for control of particle size, dopant concentration and surface chemistry.
  In Chapter 4 we attempt to provide control of the dopant location through the development of a monolayer doping method. The method sees the design of a molecular dopant precursor scaffold with self-capping properties which forms a monolayer on the precursor intrinsic SiNPs and allows for the shallow thermal-diffusion of dopants. This chapter lays the ground work for precise control over dopant location.
  Finally, Chapter 5 summarizes the findings from the previous chapters and further explores relevant future research directions.

• Subjects / Keywords

  • quantum dots
  • silicon nanoparticles
  • silicon
  • nanocrystals
  • doping

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-er21-kb70

• License

  This thesis is made available by the University of Alberta Library 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.