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Title: A predictive model of shell morphology in CdSe/CdS core/shell quantum dots

Abstract

Lattice mismatch in core/shell nanoparticles occurs when the core and shell materials have different lattice parameters. When there is a significant lattice mismatch, a coherent core-shell interface results in substantial lattice strain energy, which can affect the shell morphology. The shell can be of uniform thickness or can be rough, having thin and thick regions. A smooth shell minimizes the surface energy at the expense of increased lattice strain energy and a rough shell does the opposite. A quantitative treatment of the lattice strain energy in determining the shell morphology of CdSe/CdS core/shell nanoparticles is presented here. We use the inhomogeneity in hole tunneling rates through the shell to adsorbed hole acceptors to quantify the extent of shell thickness inhomogeneity. The results can be understood in terms of a model based on elastic continuum calculations, which indicate that the lattice strain energy depends on both core size and shell thickness. The model assumes thermodynamic equilibrium, i.e., that the shell morphology corresponds to a minimum total (lattice strain plus surface) energy. Comparison with the experimental results indicates that CdSe/CdS nanoparticles undergo an abrupt transition from smooth to rough shells when the total lattice strain energy exceeds about 27 eV or themore » strain energy density exceeds 0.59 eV/nm{sup 2}. We also find that the predictions of this model are not followed for CdSe/CdS nanoparticles when the shell is deposited at very low temperature and therefore equilibrium is not established.« less

Authors:
Publication Date:
OSTI Identifier:
22415387
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 141; Journal Issue: 19; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CADMIUM SELENIDES; CADMIUM SULFIDES; COMPARATIVE EVALUATIONS; CRYSTAL DEFECTS; LATTICE PARAMETERS; NANOPARTICLES; QUANTUM DOTS; STRAINS; SURFACE ENERGY; THICKNESS

Citation Formats

Gong, Ke, and Kelley, David F., E-mail: dfkelley@ucmerced.edu. A predictive model of shell morphology in CdSe/CdS core/shell quantum dots. United States: N. p., 2014. Web. doi:10.1063/1.4901428.
Gong, Ke, & Kelley, David F., E-mail: dfkelley@ucmerced.edu. A predictive model of shell morphology in CdSe/CdS core/shell quantum dots. United States. https://doi.org/10.1063/1.4901428
Gong, Ke, and Kelley, David F., E-mail: dfkelley@ucmerced.edu. Fri . "A predictive model of shell morphology in CdSe/CdS core/shell quantum dots". United States. https://doi.org/10.1063/1.4901428.
@article{osti_22415387,
title = {A predictive model of shell morphology in CdSe/CdS core/shell quantum dots},
author = {Gong, Ke and Kelley, David F., E-mail: dfkelley@ucmerced.edu},
abstractNote = {Lattice mismatch in core/shell nanoparticles occurs when the core and shell materials have different lattice parameters. When there is a significant lattice mismatch, a coherent core-shell interface results in substantial lattice strain energy, which can affect the shell morphology. The shell can be of uniform thickness or can be rough, having thin and thick regions. A smooth shell minimizes the surface energy at the expense of increased lattice strain energy and a rough shell does the opposite. A quantitative treatment of the lattice strain energy in determining the shell morphology of CdSe/CdS core/shell nanoparticles is presented here. We use the inhomogeneity in hole tunneling rates through the shell to adsorbed hole acceptors to quantify the extent of shell thickness inhomogeneity. The results can be understood in terms of a model based on elastic continuum calculations, which indicate that the lattice strain energy depends on both core size and shell thickness. The model assumes thermodynamic equilibrium, i.e., that the shell morphology corresponds to a minimum total (lattice strain plus surface) energy. Comparison with the experimental results indicates that CdSe/CdS nanoparticles undergo an abrupt transition from smooth to rough shells when the total lattice strain energy exceeds about 27 eV or the strain energy density exceeds 0.59 eV/nm{sup 2}. We also find that the predictions of this model are not followed for CdSe/CdS nanoparticles when the shell is deposited at very low temperature and therefore equilibrium is not established.},
doi = {10.1063/1.4901428},
url = {https://www.osti.gov/biblio/22415387}, journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 19,
volume = 141,
place = {United States},
year = {2014},
month = {11}
}