  We report the structural and electrical characterization of tungsten oxides
formed by illuminating multi-layer tungsten diselenide (WSe2) nanosheets with
an intense laser beam in the ambient environment. A noninvasive microwave
impedance microscope (MIM) was used to perform electrical imaging of the
samples. The local conductivity ~100 S/m of the oxidized product, measured by
the MIM and conventional transport experiments, is much higher than that of the
pristine WSe2, suggesting the formation of sub-stoichiometric WO3-x
polycrystals with n-type carriers. With further efforts to improve the
conductivity of the oxides, the laser-assisted oxidation process may be useful
for patterning conductive features on WSe2 or forming electrical contacts to
various transition metal dichalcogenides.
