As electronics become more and more miniaturised, there is much interest in increasing knowledge about the electronic and transport properties of nano-systems. In particular, there has been some focus on understanding the physics of nanowires with prescribed properties. Two different groups of systems have been considered that of 1D organic molecular nanowires and 2D interconnects based on graphene. In order to develop a deeper insight of the factors that determine the electronic structure and consequently the electrical transport properties, it is desirable to carry out computer simulation studies of these systems. The work reported in this thesis has focused on studying the porphyrin and DNA molecules as well as investigating the consequences of engineered 2D graphene interconnect. The latter class of systems has included graphene nanoribbons (GNRs), graphene sheets with grain boundaries (GGBs) and graphene nanomeshes (GNMs). The methodology was to use self-consistent extended Hückel theory (SC-EHT) and density functional theory (DFT) in combination with non-equilibrium Green functions (NEGFs) formalism to investigate the electronic and transport properties of these systems. The SC-EHT calculations were performed using an in-house developed C++ code named EHTransport. While the SIESTA package was employed for the DFT. It was found that the SC-EHT approach produced comparable results with that obtained by DFT. This supports the idea that the semi-empirical methods can be as valid as ab-initio approaches. The findings demonstrated that porphyrin, DNA, and graphene based systems are very promising candidates to incorporate in future electronics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:611039 |
| Date | January 2014 |
| Creators | Elias, Watheq Zako |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/60045/ |
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