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Conversion of amorphous TiO2 coatings into their crystalline form using a novel microwave plasma treatment
Date Issued
2011-07-25
Date Available
2011-04-15T09:06:38Z
Abstract
Crystalline titanium dioxide (TiO2) coatings have been widely used in photo-electrochemical solar cell applications. In this study, TiO2 and carbon-doped TiO2 coatings were deposited onto unheated titanium and silicon wafer substrates using a DC closed-field magnetron sputtering system. The resultant coatings had an amorphous structure and a post-deposition heat treatment is required to convert this amorphous structure into the photoactive crystalline phase(s) of TiO2. This study investigates the use of a microwave plasma heat treatment as a means of achieving this crystalline conversion. The treatment involved placing the sputtered coatings into a 2.45 GHz microwave-induced nitrogen plasma where they were heated to approximately 550°C. It was observed that for treatment times as short as 1 minute, the 0.25-µm thick coatings were converted into the anatase crystalline phase of TiO2. The coatings were further transformed into the rutile crystalline phase after treatments at higher temperatures. The doping of TiO2 with carbon was found to result in a reduction in this phase transformation temperature, with higher level of doping (up to 5.8% in this study) leading to lower anatase-to-rutile transition temperature. The photoactivity performance of both doped and un-doped coatings heat-treated using both furnace and microwave plasma was compared. The carbon-doped TiO2 exhibited a 29% increase in photocurrent density compared to that observed for the un-doped coating. Comparing carbon-doped coatings heat-treated using the furnace and microwave plasma, it was observed that the latter yielded a 19% increase in photocurrent density. This enhanced performance may be correlated to the differences in the coatings’ surface morphology and band gap energy, both of which influence the coatings’ photoabsorption efficiency.
Sponsorship
Science Foundation Ireland
Type of Material
Journal Article
Publisher
Elsevier
Journal
Surface and Coatings Technology
Volume
205
Issue
Supplement 2
Start Page
S235
End Page
S240
Copyright (Published Version)
2010 Published by Elsevier B.V.
Subject – LCSH
Titanium dioxide films
Magnetrons
Sputtering (Physics)
Microwave plasmas
Phase transformations (Statistical physics)
Web versions
Language
English
Status of Item
Peer reviewed
ISSN
0257-8972
This item is made available under a Creative Commons License
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