Supersonic cluster beam deposition of nanostructured titania |
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Authors: | E Barborini I N Kholmanov A M Conti P Piseri S Vinati P Milani and C Ducati |
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Institution: | (1) INFM, Dipartimento di Fisica, Università di Milano, Via Celoria 16, 20133 Milano, Italy;(2) Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 IPZ, UK |
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Abstract: | Nanostructured titanium dioxide films have been deposited
by supersonic cluster beam deposition (CBD). Nanoparticles are
produced by a pulsed microplasma cluster source (PMCS) and
selected by aerodynamic separation effects. The as-deposited
film is a complex mixture where amorphous material coexists, at
the nanoscale, with anatase and rutile crystal phases. The
nanocrystalline fraction of the film is characterized by crystal
size ranging from 100 nm to less than 5 nm. We have
characterized the film structure by transmission electron
microscopy, Raman spectromicroscopy, X-ray diffraction, and
UV-visible spectroscopy showing that correlations exist between
cluster size and film properties. In particular if very small
clusters are deposited, the film shows a predominant rutile
phase whereas larger clusters form films with mainly anatase
structure. Our observations suggest that phonon confinement
effects are responsible for a significant shift and broadening
observed for the Raman peaks. In addition, optical gap tuning is
provided by mass selection: large clusters assembling generates
a film with 3.22 eV optical gap, while smallest clusters 3.52
eV. |
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Keywords: | 77 84 Bw Elements oxides nitrides borides carbides chalcogenides etc 81 05 Zx New materials: theory design and fabrication 78 40 -q Absorption and reflection
spectra: visible and ultraviolet 63 22 +m Phonons or
vibrational states in low-dimensional structures and nanoscale
materials |
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