Modeling of Kinetically Limited Growth Rate for Solution-Synthesized Germanium Nanocrystals

Solution synthesis is a common method of generating semiconductor nanocrystals. For solution synthesis, many studies have assumed that the growth rate is diffusion-limited with an unphysically low diffusion constant. In this thesis, a model is developed that considers both diffusion and surface kinetics. The diffusion coefficient of Ge monomers through the solvent, octadecene, at elevated synthesis temperatures is estimated to be on the order of 10-5 to 10-4 cm2/sec, while the mass transfer boundary layer thickness is estimated to be on the order of a few nanometers, similar to the nanocrystal size. These two realistic conditions strongly suggest that the common assumption on diffusion limitation may not be warranted and that surface adsorption and desorption of growth precursors and ligands must govern the nanocrystal growth rate. The modeling incorporates the surface rate coefficients as fitting parameters, where the rate coefficients of organic ligands experimentally measured on Ge (111) surface are used as initial values. It is assumed that Ge monomers adsorb on the nanocrystal surface irreversibly. The modeling results on nanocrystal size as a function of time agree well with the experimental outcome, strongly supporting that the Ge nanocrystal growth rate is governed by the surface kinetics and not by the boundary layer diffusion.

Name thesis:degree_name

Chemical Engineering

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemical and Biological Engineering

Year dc:date.available

2014

Author dc:creator

• Shoop, Nicholas

Contributors dc:contributor

• Han, Sang
• Petsev, Dimiter
• Boyle, Timothy

• Germanium
• nanocrystal
• kinetics
• Model
• diffusion
• boundary layer

Language dc:language

English

Identifier

https://digitalrepository.unm.edu/cbe_etds/45

OAI identifier oai:identifier

oai:digitalrepository.unm.edu:cbe_etds-1044