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Charge writing on nanocrystalline tin dioxide nanoparticles. / Wing Lup David Loke

Swansea University Author: Wing Lup David Loke

Abstract

"Nanotechnology is an emerging field that shows the potential to bring the development in the various aspects of research to a new level. However, this evolution relies on the advancement in fabricating and locating material on surfaces with nanoscale precision. Self assembly is believed to be...

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Published: 2007
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42743
first_indexed 2018-08-02T18:55:26Z
last_indexed 2018-08-03T10:10:58Z
id cronfa42743
recordtype RisThesis
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spelling 2018-08-02T16:24:30.3050039 v2 42743 2018-08-02 Charge writing on nanocrystalline tin dioxide nanoparticles. 19db3cc00b453d79178297679ab44e9a NULL Wing Lup David Loke Wing Lup David Loke true true 2018-08-02 "Nanotechnology is an emerging field that shows the potential to bring the development in the various aspects of research to a new level. However, this evolution relies on the advancement in fabricating and locating material on surfaces with nanoscale precision. Self assembly is believed to be the solution to overcome the challenges and is presently being pursued in various guises, one of which is nanopatteming. Nanocrystalline tin dioxide is an n-type wide band gap semiconductor, which is commonly used for gas sensing applications. In Swansea University, the research on gas sensors had led to the discovery that by applying negative voltage pulses from a Scanning Tunnelling Microscope (STM) tip, it is possible to pattern the 8nm nanocrystalline tin dioxide grains. This results in features that are of average size of about 5nm in height and 17nm in width. Further research reveals that close to 100% success rate can be obtained with -6.0V tip voltage for 100?s, and the features patterned could be erased by scanning with a positive tip voltage. Moreover, the apparent height of the features on STM scans is dependent on the scanning tip voltage; and the grid Scanning Tunnelling Spectroscopy (STS) revealed a higher current flow into the patterned features. These experiments are in agreement and suggest that the patterned features are electronic in nature, as opposed to topographic. This thesis investigates the nanopatteming phenomena exhibited by tin dioxide grains at high temperature using the techniques of STM/STS, and with the aid of oxidising and reducing gases. At elevated temperature, nanopatteming on tin dioxide reveals a "charge spreading" effect, resulting in bigger feature size and lower current flowing through the patterned features. The studies also demonstrated the possibility to trigger the charge writing mechanism whilst scanning with a higher magnitude of tip voltage, charging large areas of the surface. The research on gas exposures with oxygen (oxidising) and carbon monoxide (reducing) gas favours the proposal that patterned features are electronic in nature; as well as acting as a feasibility study for the possibility of using the patterns for molecular docking applications. The investigation on the erasing process showed that a high magnitude voltage will result in removal of individual charged tin dioxide grains from the surface instead of extraction of electrons. Suggestions for future work that could be explored based on the findings presented in this study are presented in the last section of the thesis." E-Thesis Materials science.;Nanotechnology. 31 12 2007 2007-12-31 COLLEGE NANME Engineering COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:30.3050039 2018-08-02T16:24:30.3050039 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Wing Lup David Loke NULL 1 0042743-02082018162518.pdf 10807512.pdf 2018-08-02T16:25:18.4770000 Output 25021785 application/pdf E-Thesis true 2018-08-02T16:25:18.4770000 false
title Charge writing on nanocrystalline tin dioxide nanoparticles.
spellingShingle Charge writing on nanocrystalline tin dioxide nanoparticles.
Wing Lup David Loke
title_short Charge writing on nanocrystalline tin dioxide nanoparticles.
title_full Charge writing on nanocrystalline tin dioxide nanoparticles.
title_fullStr Charge writing on nanocrystalline tin dioxide nanoparticles.
title_full_unstemmed Charge writing on nanocrystalline tin dioxide nanoparticles.
title_sort Charge writing on nanocrystalline tin dioxide nanoparticles.
author_id_str_mv 19db3cc00b453d79178297679ab44e9a
author_id_fullname_str_mv 19db3cc00b453d79178297679ab44e9a_***_Wing Lup David Loke
author Wing Lup David Loke
author2 Wing Lup David Loke
format E-Thesis
publishDate 2007
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 "Nanotechnology is an emerging field that shows the potential to bring the development in the various aspects of research to a new level. However, this evolution relies on the advancement in fabricating and locating material on surfaces with nanoscale precision. Self assembly is believed to be the solution to overcome the challenges and is presently being pursued in various guises, one of which is nanopatteming. Nanocrystalline tin dioxide is an n-type wide band gap semiconductor, which is commonly used for gas sensing applications. In Swansea University, the research on gas sensors had led to the discovery that by applying negative voltage pulses from a Scanning Tunnelling Microscope (STM) tip, it is possible to pattern the 8nm nanocrystalline tin dioxide grains. This results in features that are of average size of about 5nm in height and 17nm in width. Further research reveals that close to 100% success rate can be obtained with -6.0V tip voltage for 100?s, and the features patterned could be erased by scanning with a positive tip voltage. Moreover, the apparent height of the features on STM scans is dependent on the scanning tip voltage; and the grid Scanning Tunnelling Spectroscopy (STS) revealed a higher current flow into the patterned features. These experiments are in agreement and suggest that the patterned features are electronic in nature, as opposed to topographic. This thesis investigates the nanopatteming phenomena exhibited by tin dioxide grains at high temperature using the techniques of STM/STS, and with the aid of oxidising and reducing gases. At elevated temperature, nanopatteming on tin dioxide reveals a "charge spreading" effect, resulting in bigger feature size and lower current flowing through the patterned features. The studies also demonstrated the possibility to trigger the charge writing mechanism whilst scanning with a higher magnitude of tip voltage, charging large areas of the surface. The research on gas exposures with oxygen (oxidising) and carbon monoxide (reducing) gas favours the proposal that patterned features are electronic in nature; as well as acting as a feasibility study for the possibility of using the patterns for molecular docking applications. The investigation on the erasing process showed that a high magnitude voltage will result in removal of individual charged tin dioxide grains from the surface instead of extraction of electrons. Suggestions for future work that could be explored based on the findings presented in this study are presented in the last section of the thesis."
published_date 2007-12-31T04:24:11Z
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score 11.453587

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