Master of Science (MSc)
Faculty of Science
Ian P. Hamilton
Marek S. Wartak
Due to quantum dot’s ability to emit photons when subjected to light of sufficient energy, they have become optimal candidates for biomedical research and for optoelectronic applications. Fascination towards quantum dots arises from the fact that their properties are easily fine-tuned through a variety of different techniques. Electronic doping is a popular technique used to control the properties of quantum dots through the addition of different elements.
Via density functional theory calculations, this work investigated how the structural energies and HOMO-LUMO gaps were altered by the addition of impurity atoms. First, interstitial and substitutional doping styles were investigated at 0 K for a CdSe quantum dot that contained a single Ag+ impurity ion, and it was concluded that the interstitial doping style was more structurally favourable than substitutional doping. In addition, different dopant locations were analyzed and it was determined that interstitially doped structures with Ag+ ions in surface site locations were approximately 1 eV more structurally favourable than structures with dopant ions placed midway in the structure and at the core.
To maintain charge neutrality after the addition of a Ag+ ion, a Cl- ion was added to the surface and it was determined that the closer the two atoms were on the surface the more structurally stable the quantum dot was at 0 K. Also, the HOMO-LUMO gaps for those structures were larger by approximately 0.5 eV compared to the structures where the two atoms were placed farthest apart on the surface.
At a finite temperature value of 333 K, there were no trends visible between the HOMO-LUMO gaps, structural energies, and the distance between the 2 atoms. It was however concluded that all doped structures were more energetically favourable than their undoped counterpart at both temperature values of 0 and 333 K.
Gaebler, Heather, "A Computational Study of Silver Doped CdSe Quantum Dots" (2017). Theses and Dissertations (Comprehensive). 1980.