Date of Award
Winter 12-15-2014
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
This dissertation reports the novel synthesis of PbS quantum plates (QPs) via a reaction executed at low temperatures. The PbS QPs are grown in a template-assisted mechanism, with the first excitonic peak observed in the visible region of light at ~620 nm (2.0 eV), at an energy radically different than the band gap of bulk PbS (~3000 nm, 0.42eV). The large energy shift is due to the extremely thin dimension of these nanoplates, which is determined to be ~1 nm in thickness. Thickness measurements are made in a powder X-ray diffractometer (XRD) at low angles (between 2-15º 2θ). These measurements show a series of reflections in highly lamellar structures and give a spacing easily calculated using a modified version of the Bragg diffraction equation and applied to a straight line. During experimentation, a discrepancy was noticed while observing the lamellar template under various conditions. The TEM consistently showed an expanded d spacing of lamellar templates that does not fit with data from the XRD. The high vacuum atmosphere of the electron microscope induces a consistent expansion of template systems, as shown here for the first time, and proven from multiple previously published results.
An improvement on CdSe quantum wire (QW) growth using alternate synthetic procedures and shell growth avenues is also reported. Also presented here are the underlying fundamentals for a new shell growth opportunity with a previously overlooked material: MgSe. Quantum wires made from CdSe are uniquely accommodating to MgSe as a shell material due to its intrinsic properties: much closer lattice parameters versus CdSe's current widely used shell (CdS), a highly insulating band gap (4.0 eV), and the ability to be grown in many of the common semiconductor crystal structures (rock salt, zinc blende, and wurtzite).
Language
English (en)
Chair and Committee
William E. Buhro
Committee Members
Richard A. Loomis, John R. Bleeke, Julio M. D'Arcy, Li Yang
Recommended Citation
Morrison, Paul James, "Synthesis and Characterization of PbS Quantum Sheets Through Lamellar Assembly, and Updates to the CdSe Quantum Wire Synthesis" (2014). Arts & Sciences Electronic Theses and Dissertations. 352.
https://openscholarship.wustl.edu/art_sci_etds/352
Comments
Permanent URL: https://doi.org/10.7936/K7NZ85TN