electron mode using an FEI Magellan system at an accelerating voltage
of 2 keV.
For the identification of crystalline phases in the TiO2 layers, glancing
angle X-ray diffraction (GAXRD) under an angle of incidence of 1° was
carried out on the samediffractometer systemas used for XRRmeasurements.
At small angles of incidence the penetration depth of the x-rays
is confined to the near surface area; hence, contributions from the substrate
are mostly suppressed.
The composition of the main constituents Ti and O has been
quantified by wavelength-dispersive x-ray fluorescence spectroscopy
(WDXRF) on a Bruker AXS S8 spectrometer. The Bruker AXS software
ML Quant was used to calculate the stoichiometry of the TiO2 layers.
Based on a layer model, this software package calculates the reabsorption
and secondary fluorescence contributions to the primary
fluorescence yield for a layered and hence vertically inhomogeneous
sample.
Residual carbon and nitrogen contents of the films were measured
by x-ray photoelectron spectroscopy (XPS) on a Specs Phoibos 150
MCD-9 system with Al Kα x-ray source.
To distinguish between surface carbon contamination and carbon
incorporated in the films during deposition, the surface was cleaned
in situ by argon ion sputtering for 30 s at an ion energy of 5 kV. The
XPS peak positions were calibrated using the C-C bond signal with
a C 1 s binding energy of 284.5 eV.