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Nucleation and Growth, Defect Structure, and Dynamical Behavior of Nanostructured Materials

Hubartt, Bradley C
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1416828345

Abstract Details

2014, Doctor of Philosophy, University of Toledo, Physics.
In this thesis, the nucleation, growth, defect structure, and dynamical behavior of a variety of different nanoscale systems and processes, ranging from nanoparti- cle self-assembly to multilayer metal thin-film growth to nanocolumns, are studied. In our simulations, a variety of different methods have been used including rate- equations, molecular dynamics, and analytical methods. In addition, a new compu- tational method to use graphical processing units (GPUs) to improve the efficiency of accelerated dynamics calculations is described. In the first project, which was motivated by experiments on colloidal nanoparticle (NP) island growth, the development of a self-consistent rate-equation (RE) approach to irreversible island growth and nucleation which takes into account cluster mobility and coalescence is presented. As a first application, we consider the irreversible growth of compact submonolayer islands on a two-dimensional (2D) substrate in the presence of monomer deposition as well as monomer and island diffusion. Our results are compared with kinetic Monte Carlo simulations for different values of the exponent µ describing the dependence of the island diffusion constant on island size. We find excellent agreement between our self-consistent RE results and simulation results for the island and monomer densities, up to and somewhat beyond the coverage corresponding to the peak island density. We also find good agreement between our self-consistent RE and simulation results for the portion of the island size distribution (ISD) corresponding to island sizes less than the average island size S. Our self- consistent RE approach also demonstrates that geometric effects play a crucial role in determining the power-law behavior of the ISD for µ = 1. We then present simulation results for the critical island size, stability, and mor- phology of 2D colloidal Au nanoparticle islands formed during drop-drying, which were carried out in order to explain recent experiments. Our results were obtained by carrying out molecular dynamics simulations and energetics calculations using an empirical potential which takes into account Van der Waals core-core, ligand-ligand, and ligand-solvent interactions. Good agreement with experiment is obtained for the dependence of the critical island size on NP diameter. Our results for the criti- cal length-scale for smoothing via edge diffusion are also consistent with the limited facet size and island relaxation observed in experiments. In addition, the relatively high rate of monomer diffusion on an island as well as the low barrier for interlayer diffusion are consistent with experimental observations that second-layer growth does not occur until after the first layer is complete. In order to understand the surface morphology and microstructure in glancing- angle deposition (GLAD), we have also developed and applied a method to carry out large-scale molecular dynamics simulations of Cu/Cu(100) growth up to 20 mono- layers (ML) for deposition angles ranging from 50¿ to 85¿ and for both random and fixed azimuthal angles. A variety of quantities including the porosity, roughness, lat- eral correlation length, average grain size, strain, and defect concentration were used to characterize the thin-film morphology. In good qualitative agreement with recent experiments, we find that the average strain is initially compressive but becomes ten- sile after the onset of columnar growth. Our simulations also reveal that for large deposition angles a variety of unexpected and complex dynamical processes play a key role in determining the evolution of the surface morphology and microstructure. In particular, large-amplitude oscillations in the columnar growth regime as well as large-scale re-arrangement events play a key role in promoting rapid coalescence, thus significantly enhancing the coarsening process. Finally, in order to understand the large amplitude oscillations observed in our simulations of GLAD thin-film growth, we have also carried out a systematic study of the thermomechanical properties of highly defected, tilted copper nanocolumns. Surprisingly, we find that the large defect density and compressive strain lead to ultra-low activation energies for plastic deformation via collective shear motion. As a result, the oscillation amplitude is independent of temperature. In particular, at low temperatures it can be more than 200 times the prediction of thermal elasticity theory. We also demonstrate that this leads to a new mechanism for large-amplitude thermally-induced nanocolumn oscillation in which the dynamics corresponds to a sequence of activated events which are correlated due to the motion of the entire nanocolumn.
Jacques Amar (Advisor)
Sanjay Khare (Committee Member)
Bo Gao (Committee Member)
Randall Ellingson (Committee Member)
Terry Bigioni (Committee Member)
146 p.
Condensed Matter Physics; Physics
nanocolumn, nanoparticle, thin-film, glancing-angle deposition, rate-equation, molecular dynamics

Recommended Citations

Citations

  • Hubartt, B. C. (2014). Nucleation and Growth, Defect Structure, and Dynamical Behavior of Nanostructured Materials [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1416828345

    APA Style (7th edition)

  • Hubartt, Bradley. Nucleation and Growth, Defect Structure, and Dynamical Behavior of Nanostructured Materials. 2014. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1416828345.

    MLA Style (8th edition)

  • Hubartt, Bradley. "Nucleation and Growth, Defect Structure, and Dynamical Behavior of Nanostructured Materials." Doctoral dissertation, University of Toledo, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1416828345

    Chicago Manual of Style (17th edition)

toledo1416828345
372
© 2014, some rights reserved.Creative Commons License Nucleation and Growth, Defect Structure, and Dynamical Behavior of Nanostructured Materials by Bradley C Hubartt is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Toledo and OhioLINK.