Morphology Control, Surface Functionalization and Optical Response of Silicon Nanocrystals

• Author / Creator

  Yang, Zhenyu

• As one of the most commonly applied semiconductors, nanostructured silicon has received considerable attention over the past several decades due to its suitable band gap for light harvesting (1.2 eV for bulk crystal and up to 1.9 eV for nanocrystals), unique tunable photoluminescence (PL) and high biocompatibility and low toxicity. Significant effort has been made to fabricate and optimize silicon nanocrystal (SiNC) based devices. However, numerous important fundamental questions still remain. Therefore, this thesis mainly focuses on the elucidation of several fundamental research topics in the SiNC area, including nanocrystalline morphology control and evolution, surface functionalization and corresponding optical response of SiNCs, as well as the synthesis of particle/polymer hybrid materials. The thesis starts with an introduction about physical and chemical properties of SiNCs, general synthetic approaches, the present strategies of morphology control, as well as numerous surface modification approaches. Then details of a convenient method for preparing alkyl-functionalized silicon nanocubes are provided in Chapter Two with discussions about the mechanism of the particle size and shape control. Chapter Three focuses on the “one-pot” synthesis of homogenous SiNC/polystyrene hybrid materials. Also, three prototype micro/nano structures were fabricated for the demonstration of the utility of material hybrid characteristics such as bright photoluminescence (PL), high solvent processability and chemical stability. In Chapter Four, surface functionalization of SiNCs via thermally induced hydrosilylation is reexamined. The successful ligand functionalization processed at various temperatures under air atmosphere and the formation of ligand oligomers on SiNCs were noticed. These strongly suggest that an alternative mechanism exists to promote low temperature thermal hydrosilyaltion as well as ligand oligomerization on SiNCs. The potential influence of surface oxide species on SiNC optical properties is further described in Chapter Five. Based on a systematic study, it is clear that the surface defects or traps created by suboxides are strongly relevant to the non-phonon assisted nanosecond PL lifetime decay found from yellow/orange emitting ligand-functionalized SiNCs. Finally, Chapter Six presents the conclusions of each chapter and some recommended future work relative to SiNC science.

• Subjects / Keywords

  • Morphology Control
  • Silicon Nanocrystal
  • Photoluminescence
  • Surface Functionalization

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3D795N3F

• 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.