3.2. Film properties
The TiO2 films have been characterized with respect to composition,
microstructure, morphology and optical properties.
3.2.1. Composition
The composition is quantified regarding the main constituents Ti
and O byWDXRF. The analysis of the Ti Kα1, Ti Kα2 and O Kα1 fluorescence
line intensities yields for all samples an atomic composition
of Ti: 33.6 ± 0.8 at.% and O: 66.4 ± 0.8 at.%, which represents stoichiometric
TiO2. Photoelectron spectroscopy was used to detect residual
carbon and nitrogen from possibly incomplete precursor
molecule dissociation. Since XPS is very sensitive to the surface of
the specimen, atmospheric contaminations contribute strongly. To
clean the surface from atmospheric carbon-containing species, Ar
ion sputtering was carried out. Due to preferential sputtering, the
layer composition is however altered, and the Ti/O ratio obtained
in this way is not comparable to results yielded by WDXRF. XPS results
show that after sputter cleaning carbon is present in all samples
in concentrations of 1 at.% or lower. Nitrogen was detected with increasing
concentrations for increasing substrate temperatures with
a maximum value of about 6 ± 2 at.% at TS = 320 °C.