The discrete dipole approximation with surface interaction for evanescent wave-based characterization of nanostructures on a surface with validation against experimental results

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Title The discrete dipole approximation with surface interaction for evanescent wave-based characterization of nanostructures on a surface with validation against experimental results
Publication Type thesis
School or College College of Mines & Earth Sciences
Department Metallurgical Engineering
Author Short, Mitchell R.
Date 2013-08
Description Nanotechnology has become so widely used it can be found in every aspect of life, from cell-phones and computers, to cars, and even athletic socks. As it permeates so many markets, the need for supplemental technologies has also increased. One such needed technology is in the area of nanoscale characterization. Current imaging methods are advanced; however, they do not have the capabilities to characterize the size, shape, composition, and arrangement of nanostructures and nanoparticles in a real-time, unobtrusive manner. The Polarized-Surface-Wave-Scattering system (PSWSS) is a method being researched at the University of Utah that can provide such characterization, although in order for the PSWSS to function accurately through inversion techniques, a predictive forward model must be developed and validated. This work explores the discrete dipole approximation with surface interaction (DDA-SI), an open source MATLAB toolbox, as a predictive model to calculate electromagnetic scattering by objects on a surface illuminated by an evanescent wave generated by total internal reflection (TIR). Far-field scattering predictions via DDA-SI are validated against scaled microwave experimental results for two objects on a surface: a sphere with a diameter of A/1.92 and a cube with a side length of A/1.785, where A refers to the wavelength. A good agreement between experiments and simulations is observed, especially when modified Fresnel reflection coefficients are employed by DDA-SI. Programs to calculate the amplitude scattering matrix and Mueller matrix elements have been also been created. Additionally, the sensitivity of four Mueller matrix elements (Mu, M 12, Mu, and M22) to the particle size, material (gold and silver), shape (sphere and cube), and interparticle spacing, is analyzed. It is found that these four elements are sensitive to changes in shape and interparticle spacing, whereas prove insufficient to difference in material and sizes smaller than one-half the wavelength of incident light. Findings show that DDA-SI is a strong forward model for calculation of far-field scattering, but for characterization purposes, other Mueller matrix elements that measure changes in circular polarization must be analyzed. Future research efforts will include more extensive experimental measurements and calibration, as well as creation of a scattering profile database, and further sensitivity analysis using DDA-SI.
Type Text
Publisher University of Utah
Subject Characterization; Discrete dipole approximation; Evanescent waves; Microwave analog experiments; Mueller matrix elements
Dissertation Institution University of Utah
Dissertation Name Master of Science
Language eng
Rights Management Copyright © Mitchell R. Short 2013
Format application/pdf
Format Medium application/pdf
Format Extent 969,536 bytes
Identifier etd3/id/2585
ARK ark:/87278/s6nk6p6h
Setname ir_etd
ID 196161
Reference URL https://collections.lib.utah.edu/ark:/87278/s6nk6p6h
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