Doping-induced Ti<sup>3+</sup> state and oxygen vacancies in TiO<inf>2</inf>: A single-chip combinatorial investigation

Elrahoumi, R; Zhu, L; Wagner, E; Maudez, W; Benvenuti, G; Phillips, MR; Ton-That, C

Doping-induced Ti<sup>3+</sup> state and oxygen vacancies in TiO<inf>2</inf>: A single-chip combinatorial investigation

Elrahoumi, R Zhu, L Wagner, E Maudez, W Benvenuti, G Phillips, MR Ton-That, C

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Publisher:: ELSEVIER SCIENCE SA
Publication Type:: Journal Article
Citation:: Materials Chemistry and Physics, 2023, 308
Issue Date:: 2023-10-15

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Field	Value	Language
dc.contributor.author	Elrahoumi, R
dc.contributor.author	Zhu, L
dc.contributor.author	Wagner, E
dc.contributor.author	Maudez, W
dc.contributor.author	Benvenuti, G
dc.contributor.author	Phillips, MR
dc.contributor.author	Ton-That, C https://orcid.org/0000-0003-3276-1739
dc.date.accessioned	2024-02-13T01:30:09Z
dc.date.available	2024-02-13T01:30:09Z
dc.date.issued	2023-10-15
dc.identifier.citation	Materials Chemistry and Physics, 2023, 308
dc.identifier.issn	0254-0584
dc.identifier.issn	1879-3312
dc.identifier.uri	http://hdl.handle.net/10453/175632
dc.description.abstract	TiO2 is widely recognized as a high performance photocatalyst for photocatalytic applications. Oxygen vacancies (VO) and titanium defects are known to make a significant contribution to the enhanced photocatalytic efficiency of TiO2, accordingly control of these two centers is pivotal to optimizing the surface photochemical activity. In this work, the formation of VO and Ti3+ ions induced by n-type doping of TiO2 with Nb is demonstrated using a combinatorial investigation approach. Chemical Beam Vapour Deposition (CBVD) is used to fabricate Nb concentration-graded (NbxTi1-x)O2 anatase films with 0.009 ≤ x ≤ 0.033 over a 5 mm length on a single chip. Cathodoluminescence (CL) microanalysis shows the luminescence intensity decreases with increasing Nb concentration; however, the presence of a self-trapped exciton (STE) emission, characteristic of anatase TiO2, indicates that the Nb incorporation does not affect the structural properties of TiO2. Notably, the introduction of Nb donors induces the formation of the signature luminescence bands of VO and Ti3+ at 2.05 and 2.60 eV at 80 K, respectively, and their intensities rise by up to 28% with increasing Nb content. The formation of VO and Ti3+ is attributed to the effect of excess electrons locally produced by Nb donor doping. The thermal activation energies for the STE and defect-related emissions are found to be identical at 32 ± 4 meV, suggesting that the recombination kinetics is mediated by Nb donors. Significantly, we demonstrate that the near-surface VO density can be further increased by two different post-growth treatment approaches: (i) remote hydrogen plasma and (ii) low-energy electron beam irradiation (LEEBI), without effecting the valence state of Ti. Our results open opportunities to optimize the photocatalytic properties of TiO2 by defect engineering.
dc.language	English
dc.publisher	ELSEVIER SCIENCE SA
dc.relation	http://purl.org/au-research/grants/arc/DP210101146
dc.relation.ispartof	Materials Chemistry and Physics
dc.relation.isbasedon	10.1016/j.matchemphys.2023.128283
dc.rights	info:eu-repo/semantics/embargoedAccess
dc.subject	0303 Macromolecular and Materials Chemistry, 0912 Materials Engineering, 1007 Nanotechnology
dc.subject.classification	Materials
dc.subject.classification	4016 Materials engineering
dc.title	Doping-induced Ti<sup>3+</sup> state and oxygen vacancies in TiO<inf>2</inf>: A single-chip combinatorial investigation
dc.type	Journal Article
utslib.citation.volume	308
utslib.for	0303 Macromolecular and Materials Chemistry
utslib.for	0912 Materials Engineering
utslib.for	1007 Nanotechnology
pubs.organisational-group	University of Technology Sydney
pubs.organisational-group	University of Technology Sydney/Faculty of Science
pubs.organisational-group	University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	embargoed	*
utslib.copyright.embargo	2025-10-01T00:00:00+1000Z
dc.date.updated	2024-02-13T01:30:08Z
pubs.publication-status	Published
pubs.volume	308

Abstract:

TiO2 is widely recognized as a high performance photocatalyst for photocatalytic applications. Oxygen vacancies (VO) and titanium defects are known to make a significant contribution to the enhanced photocatalytic efficiency of TiO2, accordingly control of these two centers is pivotal to optimizing the surface photochemical activity. In this work, the formation of VO and Ti3+ ions induced by n-type doping of TiO2 with Nb is demonstrated using a combinatorial investigation approach. Chemical Beam Vapour Deposition (CBVD) is used to fabricate Nb concentration-graded (NbxTi1-x)O2 anatase films with 0.009 ≤ x ≤ 0.033 over a 5 mm length on a single chip. Cathodoluminescence (CL) microanalysis shows the luminescence intensity decreases with increasing Nb concentration; however, the presence of a self-trapped exciton (STE) emission, characteristic of anatase TiO2, indicates that the Nb incorporation does not affect the structural properties of TiO2. Notably, the introduction of Nb donors induces the formation of the signature luminescence bands of VO and Ti3+ at 2.05 and 2.60 eV at 80 K, respectively, and their intensities rise by up to 28% with increasing Nb content. The formation of VO and Ti3+ is attributed to the effect of excess electrons locally produced by Nb donor doping. The thermal activation energies for the STE and defect-related emissions are found to be identical at 32 ± 4 meV, suggesting that the recombination kinetics is mediated by Nb donors. Significantly, we demonstrate that the near-surface VO density can be further increased by two different post-growth treatment approaches: (i) remote hydrogen plasma and (ii) low-energy electron beam irradiation (LEEBI), without effecting the valence state of Ti. Our results open opportunities to optimize the photocatalytic properties of TiO2 by defect engineering.

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http://hdl.handle.net/10453/175632