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Electronic and structural properties of Au contacts on ZnO nanowires. / Alexander M Lord

Swansea University Author: Alexander M Lord

Abstract

Zinc Oxide has emerged from an unspectacular past in the field of electronics to become one of the most widely researched materials for future devices. Here we investigate the growth and electrical properties of semiconducting ZnO nanowires for future application in the field of Nano-Devices and pre...

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Published: 2013
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42804
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first_indexed 2018-08-02T18:55:35Z
last_indexed 2018-08-03T10:11:08Z
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spelling 2018-08-02T16:24:30.5233962 v2 42804 2018-08-02 Electronic and structural properties of Au contacts on ZnO nanowires. 51ba7e3f9559beba665abf14413cc735 NULL Alexander M Lord Alexander M Lord true true 2018-08-02 Zinc Oxide has emerged from an unspectacular past in the field of electronics to become one of the most widely researched materials for future devices. Here we investigate the growth and electrical properties of semiconducting ZnO nanowires for future application in the field of Nano-Devices and present a solution to control the behaviour of the electrical contacts. ZnO nanowires (NWs) from initial growth experimentation and optimisation have been thoroughly characterised both structurally and electrically. Structural characterisation revealed the high quality of nanowires from vapour phase and hydrothermal growth that translated to similar measurements of nanowire resistivity. We have confirmed the results of atomic resolution dark field imaging with simulations that no Au catalyst contaminates ZnO nanowires, which makes the material more desirable than Silicon or GaAs. Within the limits of the dark field imaging the interface of the catalyst particle and the nanowire is abrupt, clean and intimate, with no Au diffusion, interfacial layers or roughness. Electron microscopy reveals the Au has an epitaxial relationship with the ZnO and is solid during growth. Using fabrication and contamination free nanoprobe measurements (four-probe scanning tunnelling microscope) in vacuum a transition from rectifying to Ohmic is dependent on contact size and not the materials or structural variations. We have shown this with the application of the nanoprobe on free standing as-grown catalysed ZnO nanowires. Using the most common nanowire growth methods the structure has been thoroughly characterised to allow the interpretation of electrical measurements of resistivity and Au end contacts. A regime of size dependent contacts to ZnO nanowires provides the necessary knowledge and requirements to fabricate ZnO nanowire devices with controlled properties and function. This is a major hurdle for nanodevices overcome without complicated or difficult processing steps. A nanodevice can be fabricated from a substrate, with contacts, in one- step and with tailored interface properties by controlling the catalyst particle size. E-Thesis Electrical engineering.;Nanotechnology. 31 12 2013 2013-12-31 COLLEGE NANME Engineering COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:30.5233962 2018-08-02T16:24:30.5233962 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Alexander M Lord NULL 1 0042804-02082018162523.pdf 10807580.pdf 2018-08-02T16:25:23.1900000 Output 40427404 application/pdf E-Thesis true 2018-08-02T16:25:23.1900000 false
title Electronic and structural properties of Au contacts on ZnO nanowires.
spellingShingle Electronic and structural properties of Au contacts on ZnO nanowires.
Alexander M Lord
title_short Electronic and structural properties of Au contacts on ZnO nanowires.
title_full Electronic and structural properties of Au contacts on ZnO nanowires.
title_fullStr Electronic and structural properties of Au contacts on ZnO nanowires.
title_full_unstemmed Electronic and structural properties of Au contacts on ZnO nanowires.
title_sort Electronic and structural properties of Au contacts on ZnO nanowires.
author_id_str_mv 51ba7e3f9559beba665abf14413cc735
author_id_fullname_str_mv 51ba7e3f9559beba665abf14413cc735_***_Alexander M Lord
author Alexander M Lord
author2 Alexander M Lord
format E-Thesis
publishDate 2013
institution Swansea University
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
active_str 0
description Zinc Oxide has emerged from an unspectacular past in the field of electronics to become one of the most widely researched materials for future devices. Here we investigate the growth and electrical properties of semiconducting ZnO nanowires for future application in the field of Nano-Devices and present a solution to control the behaviour of the electrical contacts. ZnO nanowires (NWs) from initial growth experimentation and optimisation have been thoroughly characterised both structurally and electrically. Structural characterisation revealed the high quality of nanowires from vapour phase and hydrothermal growth that translated to similar measurements of nanowire resistivity. We have confirmed the results of atomic resolution dark field imaging with simulations that no Au catalyst contaminates ZnO nanowires, which makes the material more desirable than Silicon or GaAs. Within the limits of the dark field imaging the interface of the catalyst particle and the nanowire is abrupt, clean and intimate, with no Au diffusion, interfacial layers or roughness. Electron microscopy reveals the Au has an epitaxial relationship with the ZnO and is solid during growth. Using fabrication and contamination free nanoprobe measurements (four-probe scanning tunnelling microscope) in vacuum a transition from rectifying to Ohmic is dependent on contact size and not the materials or structural variations. We have shown this with the application of the nanoprobe on free standing as-grown catalysed ZnO nanowires. Using the most common nanowire growth methods the structure has been thoroughly characterised to allow the interpretation of electrical measurements of resistivity and Au end contacts. A regime of size dependent contacts to ZnO nanowires provides the necessary knowledge and requirements to fabricate ZnO nanowire devices with controlled properties and function. This is a major hurdle for nanodevices overcome without complicated or difficult processing steps. A nanodevice can be fabricated from a substrate, with contacts, in one- step and with tailored interface properties by controlling the catalyst particle size.
published_date 2013-12-31T03:53:41Z
_version_ 1763752669343645696
score 11.036006

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