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Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes. / Olga Kryvchenkova

Swansea University Author: Olga Kryvchenkova

Abstract

A simulation methodology to model contact and non-contact microscopy measurements has been developed within a 3-D finite element commercial device simulator by Silvaco. The tip-sample system is modelled self-consistently including tip-induced band bending and realistic tip shapes. When modelling sca...

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Published: 2015
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42291
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first_indexed 2018-08-02T18:54:21Z
last_indexed 2018-08-03T10:09:45Z
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spelling 2018-08-02T16:24:28.7137853 v2 42291 2018-08-02 Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes. ecd075a76a281ddffda70eb66fe4028e NULL Olga Kryvchenkova Olga Kryvchenkova true true 2018-08-02 A simulation methodology to model contact and non-contact microscopy measurements has been developed within a 3-D finite element commercial device simulator by Silvaco. The tip-sample system is modelled self-consistently including tip-induced band bending and realistic tip shapes. When modelling scanning tunnelling microscopy, the resulting spectra from III-V semiconductors show good agreement with experimental results and a model based on the Bardeen tunnelling approach. We have found that the image force induced barrier lowering increases the tunnelling current by three orders of magnitude when tunnelling in to the sample valence band, and by six orders of magnitude when tunnelling in to the sample conduction band. We have shown that other models which use a single weighting factor to account for image force in the conduction and valence bands are likely to underestimate the valence band current by three orders of magnitude. The role of probe shank oxide formed at the tip in air has been examined by carrying out contact and non-contact current-voltage simulations of GaAs when the probe oxide has been controllably reduced. For both contact and non-contact simulations, the contact resistance change due to oxide is dependent on polarity and as confirmed experimentally. An electrostatic tip apex interaction with an In203 thin film transistor under operation is studied using a combination of experimental electrostatic force microscopy measurements and simulations. An error in the surface potential near the drain electrode is observed in simulations due to the tip induced band bending. Two point probe measurements on ZnO nanowires and 3-D transport simulations reveal the change in the electrical behaviour of nanoscale contacts from Schottky-like to Ohmic-like when the size of Au catalyst particles is changed at the ends of free-standing ZnO nanowires in relation to the nanowire cross-section. In addition, a geometry dependent current crowding effect was analysed in the combination with self-heating calculations. Finally, we have investigated carrier confinement at the ZnO/GaZnO interface due to band offset and polarization effects. We have found that this material system is a good candidate for polarization heterostructure field effect transistors. E-Thesis Electrical engineering.;Nanotechnology. 31 12 2015 2015-12-31 COLLEGE NANME Engineering COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:28.7137853 2018-08-02T16:24:28.7137853 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Olga Kryvchenkova NULL 1 0042291-02082018162442.pdf 10797999.pdf 2018-08-02T16:24:42.8930000 Output 13835101 application/pdf E-Thesis true 2018-08-02T16:24:42.8930000 false
title Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
spellingShingle Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
Olga Kryvchenkova
title_short Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
title_full Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
title_fullStr Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
title_full_unstemmed Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
title_sort Transport simulations of ZnO nanowires and semiconductor devices in the presence of scanning probes.
author_id_str_mv ecd075a76a281ddffda70eb66fe4028e
author_id_fullname_str_mv ecd075a76a281ddffda70eb66fe4028e_***_Olga Kryvchenkova
author Olga Kryvchenkova
author2 Olga Kryvchenkova
format E-Thesis
publishDate 2015
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 A simulation methodology to model contact and non-contact microscopy measurements has been developed within a 3-D finite element commercial device simulator by Silvaco. The tip-sample system is modelled self-consistently including tip-induced band bending and realistic tip shapes. When modelling scanning tunnelling microscopy, the resulting spectra from III-V semiconductors show good agreement with experimental results and a model based on the Bardeen tunnelling approach. We have found that the image force induced barrier lowering increases the tunnelling current by three orders of magnitude when tunnelling in to the sample valence band, and by six orders of magnitude when tunnelling in to the sample conduction band. We have shown that other models which use a single weighting factor to account for image force in the conduction and valence bands are likely to underestimate the valence band current by three orders of magnitude. The role of probe shank oxide formed at the tip in air has been examined by carrying out contact and non-contact current-voltage simulations of GaAs when the probe oxide has been controllably reduced. For both contact and non-contact simulations, the contact resistance change due to oxide is dependent on polarity and as confirmed experimentally. An electrostatic tip apex interaction with an In203 thin film transistor under operation is studied using a combination of experimental electrostatic force microscopy measurements and simulations. An error in the surface potential near the drain electrode is observed in simulations due to the tip induced band bending. Two point probe measurements on ZnO nanowires and 3-D transport simulations reveal the change in the electrical behaviour of nanoscale contacts from Schottky-like to Ohmic-like when the size of Au catalyst particles is changed at the ends of free-standing ZnO nanowires in relation to the nanowire cross-section. In addition, a geometry dependent current crowding effect was analysed in the combination with self-heating calculations. Finally, we have investigated carrier confinement at the ZnO/GaZnO interface due to band offset and polarization effects. We have found that this material system is a good candidate for polarization heterostructure field effect transistors.
published_date 2015-12-31T03:52:41Z
_version_ 1763752606227759104
score 11.0128355

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