of the thin films were examined by field emission scanning electron
microscopy (SEM) (Zeiss Sigma) with an in-lens detector and 5 kV accelerating
voltage. High-angle annular dark-field scanning transmission electron
microscopy (HAADF-STEM) of the thin-film cross sections was performed
using a JEOL ARM200F TEM setup operated at 200 kV. TEM cross sections
of the thin films were prepared using focused ion beam milling. Pt
and carbon protective layers were deposited using ion-beam-induced
deposition (IBID) and electron-beam-induced deposition (EBID) to preserve
the thin-film structure during the milling process.
Structural
characterization was performed using a Bruker D8 Eco X-ray diffractometer
(XRD) with a Cu Kα (λ= 1.5406 Å) source and a Lynx-eye
detector in a grazing incidence configuration (GI-XRD) at an incident
angle of 0.5° and in the 2θ range of 20–80°.
A Thermo Scientific Kα X-ray photoelectron spectroscopy (XPS)
setup equipped with a monochromated Al Kα source (hν = 1486.6 eV) was used for the chemical analysis. The binding
energy was corrected with respect to the adventitious carbon C 1s
peak at 284.8 eV. Peak fitting was done using the Casa XPS software.
The optical absorbance of the films was characterized with a PerkinElmer
1050 UV/vis/NIR spectrophotometer in the wavelength range of 300–900
nm.