Syntheses and Optical Properties of Silicon Based Nanomaterials

• Author / Creator

  Dasog, Mita

• Silicon (Si) based nanomaterials have the potential to revolutionize the microelectronics industry by introducing desirable nanoscale properties into electronic components without compromising the material composition. They have also been proposed as a greener alternative for many Group III-V and II-VI semiconductors. However, the high temperature and costly infrastructure required for the large scale synthesis and characterization of Si based materials still poses a challenge that impedes their widespread application. This thesis describes the synthesis of silicon (Si), silicon carbide (SiC), silicon nitride (Si3N4), and silica (SiO2) nano- and micromaterials from compositionally tuned sol-gel polymers. Si based materials were prepared either via disproportionation of (RSiO1.5)n sol-gel polymers or by a magnesiothermic reduction method. Magnesiothermic reduction was carried out at the lowest temperature reported in the literature to date (500 - 600 oC) to make Si, Si3N4, and SiC materials with various morphologies.
  Detailed chemical investigations were carried out to understand the origin of blue luminescence in Si nanocrystals (NCs). It was determined that the presence of nitrogen, oxygen, and chlorine based impurities in trace amounts can lead to blue emission via a charge transfer process. Si-NCs with various surface protecting groups were synthesized in order to tune their luminescence across the visible spectrum. The luminescence is believed to originate from surface defects, and the excited state lifetimes of such emissions are short lived (a few nanoseconds). This is the first example to demonstrate emission across the visible spectrum by tuning the surface protecting groups.
  The materials and methodologies summarized in this thesis open up new avenues in the pursuit of Si nanomaterial based photovoltaics, sensors, biological applications, redox reactions, greenhouse gas sequestration, and many more.

• Subjects / Keywords

  • Silicon nanomaterials
  • Quantum dots
  • Luminescence

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3BS7J

• 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.