Femtosecond laser thinning for resistivity control of tungsten ditelluride thin-films synthesized from sol-gel deposited tungsten oxide

Abstract

In this work we present a route for fabricating WTe$_2$ thin-films together with femtosecond laser post processing, enabling to finely control the conductivity. First, we produce amorphous films of WO$_3$ on Si by spin-coating a sol-gel precursor followed by a consolidating annealing and a reduction process in partial H$_2$ atmosphere, leading to porous metallic tungsten cluster layers. To achieve WTe$_2$, the films were exposed to the chalcogen vapours by isothermal closed space vapor transport. The formation of a tungsten ditelluride film composed of piled crystals could be confirmed and a gradient of surface rich Te identified through hard X-ray photoelectron spectroscopy. Finally, it is demonstrated that resistivity can be changed from 0.2 mΩ.m to 1 mΩ.m, while keeping the material characteristics. An anisotropic conductivity can be induced by direct selective thinning with fs laser writing (350 fs pulse duration, 515 nm laser wavelength) of 1D stripes. The obtained results, demonstrate that laser processing is a promising thin-film post-processing technique that can be applied to 2D transition metal dichalcogenide thin films.