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Investigation of Structural and Electronic Aspects of Ultrathin Metal Nanowires

Electronic Theses of Indian Institute of Science

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Title Investigation of Structural and Electronic Aspects of Ultrathin Metal Nanowires
 
Creator Roy, Ahin
 
Subject Metal Nanowire
DFT Simulation
Electron Microscopy
Ultrathin Metal Nanowires
Ultrathin Nanowires
Density Functional Theory
Ultrathin Gold Nanowires
Semiconducting Wires
Ultrathin Gold Nanowire-based Sensors
FCC Metal Nanowires
Materials Science
 
Description The constant trend of device miniaturization along with ever-growing list of unusual behaviour of nanoscale materials has fuelled the recent research in fabrication and applications of ultrathin (~2 nm diameter) nanowires. Although semiconductor nanowires of this dimension is well-researched, molecular-scale single-crystalline metal nanowires have not been addressed in details. Such single crystalline Au nanowires are formed by oriented attachment of Au nanoparticles along [111] direction. A very low concentration of extended defects in these wires result in a high electrical conductivity, making them ideal for nanoscale interconnects. Other metal nanowires, e.g. Ag and Cu, have very low absorption co-efficient useful for fabrication of transparent conducting films. On the other hand, because of the reduced dimensions, there exists a tantalizing possibility of dominating quantum effects leading to their application in sensing and actuation. Also, speaking in terms of atomic structure, these systems suffer from intense surface stress, and the atomistic picture can be drastically different from bulk. Thus, although a myriad of applications are possible with ultrathin metal nanowires, a rigorous systematic knowledge of their atomic and electronic structure is not yet available. This thesis is the first one to model such computationally demanding systems with emphasis on their possible applications.

In this thesis, we have explored various structural and electronic aspects of one-dimensional ultrathin nanowires with ab initio density functional theory coupled with experiments. The merit of Au nanowires has been tested as nanoscale interconnects. From atomistic point of view, these FCC Au nanowires exhibit an intriguing relaxation mechanism, which has been explored by both theory and experiment. The primary factor governing the relaxation mechanism was found to be the anisotropic surface stress of the bounding facets, and it is extended to explain the relaxation of other metallic nanowires. Our studies suggest that AuNWs of this dimension show semiconductor-like sensitivity towards small chemical analytes and can be used as nanoscale sensors. Also, we have found that further reducing the diameter of the Au-nanowires leads to opening of a band gap.
 
Contributor Ravishankar, Narayanan
Singh, Abhishek Kumar
 
Date 2018-02-11T07:38:19Z
2018-02-11T07:38:19Z
2018-02-11
2015
 
Type Thesis
 
Identifier http://hdl.handle.net/2005/3091
http://etd.ncsi.iisc.ernet.in/abstracts/3438/G26931-Abs.pdf
 
Language en_US
 
Relation G26931