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Title: Ultrathin Amorphous Titania on Nanowires: Optimization of Conformal Growth and Elucidation of Atomic-Scale Motifs

Journal Article · · Nano Letters

Due to its chemical stability, titania (TiO2) thin films increasingly have significant impact when applied as passivation layers. However, optimization of growth conditions, key to achieving essential film quality and effectiveness, is challenging in the few-nanometers thickness regime. Furthermore, the atomic-scale structure of the nominally amorphous titania coating layers, particularly when applied to nanostructured supports, is difficult to probe. In this Letter, the quality of titania layers grown on ZnO nanowires is optimized using specific strategies for processing of the nanowire cores prior to titania coating. The best approach, low-pressure O2 plasma treatment, results in significantly more-uniform titania films and a conformal coating. Characterization using X-ray absorption near edge structure (XANES) reveals the titania layer to be highly amorphous, with features in the Ti spectra significantly different from those observed for bulk TiO2 polymorphs. Analysis based on first-principles calculations suggests that the titania shell contains a substantial fraction of under-coordinated Ti4+ ions. The best match to the experimental XANES spectrum is achieved with a “glassy” TiO2 model that contains ~50% of under-coordinated Ti4+ ions, in contrast to bulk crystalline TiO2 that only contains 6-coordinated Ti4+ ions in octahedral sites.

Research Organization:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); US Department of the Navy, Office of Naval Research (ONR)
Grant/Contract Number:
SC0012704; AC02-05CH11231
OSTI ID:
1543400
Report Number(s):
BNL-211857-2019-JAAM
Journal Information:
Nano Letters, Vol. 19, Issue 6; ISSN 1530-6984
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 8 works
Citation information provided by
Web of Science

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