Laser-assisted oxidation of multi-layer tungsten diselenide nanosheets

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 ∼10² 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 WO_3-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.