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Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification

Alex Lord Orcid Logo, Vincent Consonni Orcid Logo, Fabrice Donatini, Demie M. Kepaptsoglou Orcid Logo, Quentin M. Ramasse Orcid Logo, Jon E. Evans Orcid Logo, Martin W. Allen Orcid Logo, Mark S’ari, Mac Hathaway, Irene M. N. Groot Orcid Logo

ACS Applied Materials & Interfaces, Volume: 17, Issue: 12, Pages: 18996 - 19011

Swansea University Author: Alex Lord Orcid Logo

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DOI (Published version): 10.1021/acsami.4c17872

Abstract

Schottky diodes have been a fundamental component of electrical circuits for many decades, and intense research continues to this day on planar materials with increasingly exotic compounds. With the birth of nanotechnology, a paradigm shift occurred with Schottky contacts proving to be essential for...

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Published in: ACS Applied Materials & Interfaces
ISSN: 1944-8244 1944-8252
Published: American Chemical Society (ACS) 2025
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URI: https://cronfa.swan.ac.uk/Record/cronfa69527
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With the birth of nanotechnology, a paradigm shift occurred with Schottky contacts proving to be essential for enabling nanodevice inventions and increasing their performance by many orders of magnitude, particularly in the fields of piezotronics and piezoelectric energy harvesting. ZnO nanomaterials have proven to be the most popular materials in those devices as they possess high piezoelectric coefficients, high surface sensitivity, and low resistivity due to the high native n-type doping and low hole concentration. ZnO nanowires grown by vapor phase techniques with the aid of a metal catalyst provide a ready-made epitaxial Schottky contact free from interfacial layers and major defects. We show here with the most comprehensive experimental investigation to-date of Au nanocontacts to ZnO nanowires that the modulation of bulk and surface oxygen can dramatically increase the rectifying quality of these contacts when applied in the metal&#x2013;semiconductor&#x2013;metal (M-S-M) device configuration with potential barriers approaching the performance of planar contacts on single crystal ZnO. Before modification, the Au-ZnO nanowire contacts in a rectifying-nanowire-ohmic M-S-M device configuration typically show limited current rectification and electrical transport properties dominated by surface effects and tunneling at the contact edge. Interestingly, the oxygen modulation only has a minor effect on the resistivity as the high-resolution cathodoluminescence spectroscopy shows that the dominant donors are In, Ga, and Al with no visible band emissions often associated with detrimental point defects. The spectroscopy also revealed that carbon is incorporated into the bulk that may present interesting magnetic properties for future spintronics applications. Atomic-resolution electron microscopy confirms the Zn-polar orientation of the high-quality single crystal nanowires used for the electrical measurements. X-ray photoelectron spectroscopy shows oxygen-annealed nanowires have fewer surface oxygen defects, and when that difference is coupled with a reduction in surface oxygen vacancies via oxygen plasma treatment, the current rectification can increase by several orders of magnitude with a much lower dispersion in the effective potential barrier properties when compared to those that are not annealed. This study concludes after the electrical measurements of 66 nanowire contacts/M-S-M structures with diameters as small as 25 nm using a scanning tunneling microscopy probe that effective device potential barrier heights of 0.65 eV and on&#x2013;off ratios of 3 orders of magnitude can be achieved. Interestingly, this change in contact properties is transient in nature, revealing dynamic surface effects can govern the rectifying behavior and surface passivation techniques are desirable to achieve consistent performance. This work shows the overriding effects of surface defects and adsorbates on the sloping facets near the Au contact edge and the potential for this effect to be used to control the electrical transport properties and produce molecular-scale sensors to greatly enhance the performance of many piezotronic and energy harvesting devices.</abstract><type>Journal Article</type><journal>ACS Applied Materials &amp;amp; Interfaces</journal><volume>17</volume><journalNumber>12</journalNumber><paginationStart>18996</paginationStart><paginationEnd>19011</paginationEnd><publisher>American Chemical Society (ACS)</publisher><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint>1944-8244</issnPrint><issnElectronic>1944-8252</issnElectronic><keywords>ZnO, Nanowires, Schottky contacts, Piezotronic applications, Bulk modification, Surface modification</keywords><publishedDay>26</publishedDay><publishedMonth>3</publishedMonth><publishedYear>2025</publishedYear><publishedDate>2025-03-26</publishedDate><doi>10.1021/acsami.4c17872</doi><url/><notes/><college>COLLEGE NANME</college><CollegeCode>COLLEGE CODE</CollegeCode><institution>Swansea University</institution><apcterm>Another institution paid the OA fee</apcterm><funders>French National Research Agency through the IMINEN project (ANR-22-CE09-0032); Engineering and Physical Sciences Research Council (Grant number EP/W021080/1); NWO Talent Programme Vidi.</funders><projectreference/><lastEdited>2025-05-16T12:29:23.6845585</lastEdited><Created>2025-05-16T12:15:02.0119610</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Engineering and Applied Sciences - Materials Science and Engineering</level></path><authors><author><firstname>Alex</firstname><surname>Lord</surname><orcid>0000-0002-6258-2187</orcid><order>1</order></author><author><firstname>Vincent</firstname><surname>Consonni</surname><orcid>0000-0003-0171-8746</orcid><order>2</order></author><author><firstname>Fabrice</firstname><surname>Donatini</surname><order>3</order></author><author><firstname>Demie M.</firstname><surname>Kepaptsoglou</surname><orcid>0000-0003-0499-0470</orcid><order>4</order></author><author><firstname>Quentin M.</firstname><surname>Ramasse</surname><orcid>0000-0001-7466-2283</orcid><order>5</order></author><author><firstname>Jon E.</firstname><surname>Evans</surname><orcid>0000-0002-6511-4215</orcid><order>6</order></author><author><firstname>Martin W.</firstname><surname>Allen</surname><orcid>0000-0001-8786-6429</orcid><order>7</order></author><author><firstname>Mark</firstname><surname>S&#x2019;ari</surname><order>8</order></author><author><firstname>Mac</firstname><surname>Hathaway</surname><order>9</order></author><author><firstname>Irene M. 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spelling 2025-05-16T12:29:23.6845585 v2 69527 2025-05-16 Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification d547bad707e12f5a9f12d4fcbeea87ed 0000-0002-6258-2187 Alex Lord Alex Lord true false 2025-05-16 Schottky diodes have been a fundamental component of electrical circuits for many decades, and intense research continues to this day on planar materials with increasingly exotic compounds. With the birth of nanotechnology, a paradigm shift occurred with Schottky contacts proving to be essential for enabling nanodevice inventions and increasing their performance by many orders of magnitude, particularly in the fields of piezotronics and piezoelectric energy harvesting. ZnO nanomaterials have proven to be the most popular materials in those devices as they possess high piezoelectric coefficients, high surface sensitivity, and low resistivity due to the high native n-type doping and low hole concentration. ZnO nanowires grown by vapor phase techniques with the aid of a metal catalyst provide a ready-made epitaxial Schottky contact free from interfacial layers and major defects. We show here with the most comprehensive experimental investigation to-date of Au nanocontacts to ZnO nanowires that the modulation of bulk and surface oxygen can dramatically increase the rectifying quality of these contacts when applied in the metal–semiconductor–metal (M-S-M) device configuration with potential barriers approaching the performance of planar contacts on single crystal ZnO. Before modification, the Au-ZnO nanowire contacts in a rectifying-nanowire-ohmic M-S-M device configuration typically show limited current rectification and electrical transport properties dominated by surface effects and tunneling at the contact edge. Interestingly, the oxygen modulation only has a minor effect on the resistivity as the high-resolution cathodoluminescence spectroscopy shows that the dominant donors are In, Ga, and Al with no visible band emissions often associated with detrimental point defects. The spectroscopy also revealed that carbon is incorporated into the bulk that may present interesting magnetic properties for future spintronics applications. Atomic-resolution electron microscopy confirms the Zn-polar orientation of the high-quality single crystal nanowires used for the electrical measurements. X-ray photoelectron spectroscopy shows oxygen-annealed nanowires have fewer surface oxygen defects, and when that difference is coupled with a reduction in surface oxygen vacancies via oxygen plasma treatment, the current rectification can increase by several orders of magnitude with a much lower dispersion in the effective potential barrier properties when compared to those that are not annealed. This study concludes after the electrical measurements of 66 nanowire contacts/M-S-M structures with diameters as small as 25 nm using a scanning tunneling microscopy probe that effective device potential barrier heights of 0.65 eV and on–off ratios of 3 orders of magnitude can be achieved. Interestingly, this change in contact properties is transient in nature, revealing dynamic surface effects can govern the rectifying behavior and surface passivation techniques are desirable to achieve consistent performance. This work shows the overriding effects of surface defects and adsorbates on the sloping facets near the Au contact edge and the potential for this effect to be used to control the electrical transport properties and produce molecular-scale sensors to greatly enhance the performance of many piezotronic and energy harvesting devices. Journal Article ACS Applied Materials &amp; Interfaces 17 12 18996 19011 American Chemical Society (ACS) 1944-8244 1944-8252 ZnO, Nanowires, Schottky contacts, Piezotronic applications, Bulk modification, Surface modification 26 3 2025 2025-03-26 10.1021/acsami.4c17872 COLLEGE NANME COLLEGE CODE Swansea University Another institution paid the OA fee French National Research Agency through the IMINEN project (ANR-22-CE09-0032); Engineering and Physical Sciences Research Council (Grant number EP/W021080/1); NWO Talent Programme Vidi. 2025-05-16T12:29:23.6845585 2025-05-16T12:15:02.0119610 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering Alex Lord 0000-0002-6258-2187 1 Vincent Consonni 0000-0003-0171-8746 2 Fabrice Donatini 3 Demie M. Kepaptsoglou 0000-0003-0499-0470 4 Quentin M. Ramasse 0000-0001-7466-2283 5 Jon E. Evans 0000-0002-6511-4215 6 Martin W. Allen 0000-0001-8786-6429 7 Mark S’ari 8 Mac Hathaway 9 Irene M. N. Groot 0000-0001-9747-3522 10 69527__34294__1ee35bd9c09248f1bbbc6d18bc6dfe50.pdf 69527.VoR.pdf 2025-05-16T12:23:24.3795459 Output 5785361 application/pdf Version of Record true Copyright © 2025 The Authors.This publication is licensed under CC-BY 4.0 . true eng https://creativecommons.org/licenses/by/4.0/
title Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
spellingShingle Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
Alex Lord
title_short Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
title_full Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
title_fullStr Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
title_full_unstemmed Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
title_sort Large On–Off Enhancement of Au Nanocatalyst Contacts to ZnO Nanowires with Bulk and Surface Oxygen Modification
author_id_str_mv d547bad707e12f5a9f12d4fcbeea87ed
author_id_fullname_str_mv d547bad707e12f5a9f12d4fcbeea87ed_***_Alex Lord
author Alex Lord
author2 Alex Lord
Vincent Consonni
Fabrice Donatini
Demie M. Kepaptsoglou
Quentin M. Ramasse
Jon E. Evans
Martin W. Allen
Mark S’ari
Mac Hathaway
Irene M. N. Groot
format Journal article
container_title ACS Applied Materials &amp; Interfaces
container_volume 17
container_issue 12
container_start_page 18996
publishDate 2025
institution Swansea University
issn 1944-8244
1944-8252
doi_str_mv 10.1021/acsami.4c17872
publisher American Chemical Society (ACS)
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 - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
document_store_str 1
active_str 0
description Schottky diodes have been a fundamental component of electrical circuits for many decades, and intense research continues to this day on planar materials with increasingly exotic compounds. With the birth of nanotechnology, a paradigm shift occurred with Schottky contacts proving to be essential for enabling nanodevice inventions and increasing their performance by many orders of magnitude, particularly in the fields of piezotronics and piezoelectric energy harvesting. ZnO nanomaterials have proven to be the most popular materials in those devices as they possess high piezoelectric coefficients, high surface sensitivity, and low resistivity due to the high native n-type doping and low hole concentration. ZnO nanowires grown by vapor phase techniques with the aid of a metal catalyst provide a ready-made epitaxial Schottky contact free from interfacial layers and major defects. We show here with the most comprehensive experimental investigation to-date of Au nanocontacts to ZnO nanowires that the modulation of bulk and surface oxygen can dramatically increase the rectifying quality of these contacts when applied in the metal–semiconductor–metal (M-S-M) device configuration with potential barriers approaching the performance of planar contacts on single crystal ZnO. Before modification, the Au-ZnO nanowire contacts in a rectifying-nanowire-ohmic M-S-M device configuration typically show limited current rectification and electrical transport properties dominated by surface effects and tunneling at the contact edge. Interestingly, the oxygen modulation only has a minor effect on the resistivity as the high-resolution cathodoluminescence spectroscopy shows that the dominant donors are In, Ga, and Al with no visible band emissions often associated with detrimental point defects. The spectroscopy also revealed that carbon is incorporated into the bulk that may present interesting magnetic properties for future spintronics applications. Atomic-resolution electron microscopy confirms the Zn-polar orientation of the high-quality single crystal nanowires used for the electrical measurements. X-ray photoelectron spectroscopy shows oxygen-annealed nanowires have fewer surface oxygen defects, and when that difference is coupled with a reduction in surface oxygen vacancies via oxygen plasma treatment, the current rectification can increase by several orders of magnitude with a much lower dispersion in the effective potential barrier properties when compared to those that are not annealed. This study concludes after the electrical measurements of 66 nanowire contacts/M-S-M structures with diameters as small as 25 nm using a scanning tunneling microscopy probe that effective device potential barrier heights of 0.65 eV and on–off ratios of 3 orders of magnitude can be achieved. Interestingly, this change in contact properties is transient in nature, revealing dynamic surface effects can govern the rectifying behavior and surface passivation techniques are desirable to achieve consistent performance. This work shows the overriding effects of surface defects and adsorbates on the sloping facets near the Au contact edge and the potential for this effect to be used to control the electrical transport properties and produce molecular-scale sensors to greatly enhance the performance of many piezotronic and energy harvesting devices.
published_date 2025-03-26T05:28:25Z
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score 11.089551

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