Abstract:
Laser pyrolysis is a synthesis method used to produce
thin films and nanomaterials of high quality and purity,
by intersecting a laser beam with a chemical precursor.
We have chosen laser pyrolysis to synthesize tungsten
trioxide starting with tungsten ethoxide precursor. The
film had a thickness that varied from 205 nm to 1 μm. Xray
diffraction and Raman spectroscopy confirmed the
presence of a mixture of hexagonal and tetragonal phase
WO3 in the synthesized film, and it was clear that annealing
greatly influenced the phases and types of structures
formed. I-V curves of the films showed n-type semiconducting behaviour, but the mixed phase appeared to cause
a similar behaviour of dopants in a semiconductor. The
refractive index decreased with increasing wavelength
and gave values of up to 21 at low wavelengths. The average
optical band gap was found to 3.6 eV from UV/Vis
spectroscopy. Scanning Electron Microscopy (SEM)
showed a mixture of nano- and microstructures and
shapes formed after annealing. One of the grown
nanostructures was nanorods, this isolated using FIB for
possible applications such as an active sensing medium
in gas sensors.
