Defense Date
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Chemistry
First Advisor
Indika U. Arachchige
Abstract
Silicon and silicon-germanium alloy nanostructures have garnered increasing attention in the past 25 years due to their favorable optical properties, visible to near-IR luminescence, and inherently low toxicity. While many synthetic routes have been discussed in the literature, the high-temperature, solid-state disproportionation of hydrogen silsesquioxane (HSQ) has become the most popular way to produce highly crystalline, size-tunable Si and Si-based nanostructures (NCs). It has been shown in this work that maximum annealing temperature from 450°-1100°C and the addition of GeI2or SnCl4 precursors can be used to achieve different morphologies, alloying efficiency, and sizes. Directly annealing HSQ from 800 - 1100°C affords quasi-spherical Si NCs (3.0 – 6.7 nm) whose optical properties can be further elucidated. Modifications in Si NC electronic band structures with varying diameters were explored by comparison of emission with absorption spectra obtained from solid-state absorbance measurements. The addition of Sn in HSQ can be used to control the morphology and diameter of the nanorod (NR), allowing for control over the energy gap in by confining the material to one dimension. NRs (7.7 – 16.5 nm) were produced by annealing HSQ at 450°C and varying the SnCl4 concentration from 0.2 – 3.0 mol %. Si1-xGex NCs (x = 0 – 14.4%) were produced by annealing HSQ at 600°C for one hour to achieve optimal alloying efficiency while retaining diameters (5.9 – 7.8 nm) within the quantum-confinement regime. The complementary synthesis of HSQ and subsequent annealing establishes these procedures as viable foundations for a wide range of electronic and photonic technologies.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-8-2024