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An atomistic study on configuration,...

Shahabi, Alireza.

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An atomistic study on configuration, mechanics and growth of nanoscale filaments.

Record Type:	Electronic resources : Monograph/item
Title/Author:	An atomistic study on configuration, mechanics and growth of nanoscale filaments./
Author:	Shahabi, Alireza.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2016,
Description:	102 p.
Notes:	Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.
Contained By:	Dissertation Abstracts International78-02B(E).
Subject:	Mechanical engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10145767
ISBN:	9781369011975

An atomistic study on configuration, mechanics and growth of nanoscale filaments.
Shahabi, Alireza.

An atomistic study on configuration, mechanics and growth of nanoscale filaments. - Ann Arbor : ProQuest Dissertations & Theses, 2016 - 102 p.

Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.

Thesis (Ph.D.)--Northeastern University, 2016.

The objective of this dissertation is to study the characteristics of nanoscale materials as a function of their configuration and to investigate the nanoscale production methods, which enable us to tune their properties. Interplay between structure and function in atomically thin crystalline nanofilaments is sensitive to their conformations, size, and defect densities. At the nanoscale, dimensional confinement often creates a strong correlation between their physical properties and geometrical shape, and this is particularly important as their physical properties both influence, and are influenced by their conformations and structure.

ISBN: 9781369011975Subjects--Topical Terms:

649730
Mechanical engineering.

An atomistic study on configuration, mechanics and growth of nanoscale filaments.
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100 1 $a Shahabi, Alireza. $3 3342818
245 1 3 $a An atomistic study on configuration, mechanics and growth of nanoscale filaments.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2016
300 $a 102 p.
500 $a Source: Dissertation Abstracts International, Volume: 78-02(E), Section: B.
500 $a Adviser: Moneesh Upmanyu.
502 $a Thesis (Ph.D.)--Northeastern University, 2016.
520 $a The objective of this dissertation is to study the characteristics of nanoscale materials as a function of their configuration and to investigate the nanoscale production methods, which enable us to tune their properties. Interplay between structure and function in atomically thin crystalline nanofilaments is sensitive to their conformations, size, and defect densities. At the nanoscale, dimensional confinement often creates a strong correlation between their physical properties and geometrical shape, and this is particularly important as their physical properties both influence, and are influenced by their conformations and structure.
520 $a In the first part of the thesis, we focus on conformations of ultra-thin and ultra-long nanoscale filaments. As the synthesis lengths approach their persistence length, their conformational behavior is not unlike semi-flexible filaments. However, the ability to control their configuration is still limited and the exact relation between geometry and functions are yet to be explored. In this dissertation, we develop a novel approach to create and control the conformation of nanotubes, nanoribbons and nanowires as a method to tuning their properties. Our approach is based on controlling the boundary constraints on these nanofilaments by applying twist and displacement to their ends. We develop conformational phase diagrams by performing all-atom molecular dynamics simulations. We observe the formation of scrolled and folded nanostructures in graphene nanoribbons, and well-defined plectonemes in carbon nanotubes and silicon nanowires. We develop a stability analysis using minimization of bend and twist energies stored in the conformations, suitably modified by the long range van der Waals interactions. Our theoretical predictions are in good agreement with the molecular dynamics simulation results. In the case of graphene nanoribbons, we further investigate the effect of unpassivated edges on their structural evolution. The soft conformations in these electronically active filaments open up the possibility of non-linear stretchable interconnects, and we study their reliability by extracting the elastic stiffness of the various conformations. We extract force-displacement curves of scrolls and plectonemes in the various systems. Our analysis sheds light on the relation between the shape of the nanostructures and the elastic stiffness of the nanofilaments. In overall, our study provides us with a novel route to engineer the nanofilaments and tune their mechanical properties using a combination of physical constraints and mechanical loading.
520 $a In the next part of the dissertation, we perform a comprehensive atomistic study of the nanoscale crystal growth mechanisms of Au-catalyzed silicon nanowires grown via the vapor liquid solid method (VLS) during early stages of the droplet to nanowire transition. The transition sets the size of the nanowire, and the principles of diameter selection remain poorly understood. Our analysis reveals the role of the initial configuration of the nanodroplet and the effect of surface tension on the success of the VLS growth process. We observe lateral extension of liquid feet from the sides of nanodroplet during the VLS process. In addition to the nanodroplet diameter, the liquid feet plays a crucial role on determining the final geometry of the nanowire. We also observe an important correlation between the rate of deposition of Si atoms and presence of the twining in the nanowire structure, which significantly affects its properties. Higher deposition rates result in incorporation of metallic impurities in the nanowire structure, which consequently results in the formation of twining deformation. Our MD studies uncover a previously ignored interplay between solute trapping of catalyst particles in the nanowire, and twin formation, and we discuss this effect in the context of past experimental reports on twin formation in semiconducting nanowires, and the ability to potentially control their formation via control of gas phase conditions.
590 $a School code: 0160.
650 4 $a Mechanical engineering. $3 649730
650 4 $a Materials science. $3 543314
650 4 $a Nanoscience. $3 587832
690 $a 0548
690 $a 0794
690 $a 0565
710 2 $a Northeastern University. $b Mechanical and Industrial Engineering. $3 1035359
773 0 $t Dissertation Abstracts International $g 78-02B(E).
790 $a 0160
791 $a Ph.D.
792 $a 2016
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10145767