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Effect of the oxygen deficiency of ceramic TiO 2−x targets on the deposition of TiO 2 thin films by DC magnetron sputtering
Author(s) -
Poelman H.,
Tomaszewski H.,
Poelman D.,
Depla D.,
De Gryse R.
Publication year - 2004
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1867
Subject(s) - sputtering , analytical chemistry (journal) , x ray photoelectron spectroscopy , sputter deposition , materials science , thin film , stoichiometry , titanium , ceramic , argon , oxygen , chemistry , chemical engineering , metallurgy , nanotechnology , organic chemistry , chromatography , engineering
The sputter deposition of stoichiometric TiO 2 thin films has been investigated, in view of photocatalytic application. DC magnetron sputtering from ceramic targets in an argon/oxygen atmosphere was chosen as the deposition technique. Composite TiO 2 Ti targets with metallic Ti fraction from 0 to 70 wt% were prepared from TiO 2 and Ti powders following a standard ceramic procedure. The influence of target composition and sputter parameters on the film composition was examined by means of optical transmission measurements, XRD and XPS. From the former, optical absorption coefficients are calculated, which are used as a measure for the films' stoichiometry. Curve fitting of the Ti 2p 3/2 photoemission line yields the composition in terms of the presence of reduced species. Upon sputtering in argon, translucent layers are obtained for targets with up to 35 wt% Ti. For higher amounts, the optical absorption coefficient α at 550 nm increases and the layers become dark. With increasing metal Ti contribution and argon flow, more reduced Ti species contribute to the Ti 2p photoemission line. In reactive sputter mode, near‐stoichiometric TiO 2− x films are obtained for low oxygen mole fractions. For higher oxygen contributions, reduced Ti species are increasingly present for all targets. This reduction is ascribed to active re‐sputtering of the deposited layer by O − ions and the sputter yield difference between oxygen and titanium. Copyright © 2004 John Wiley & Sons, Ltd.