Synthesis and characterization of tungsten and tungsten oxide nanostructured films

Nanostructured tungsten and tungsten oxide films have been synthesized by pulsed laser deposition (PLD) in different atmospheres (He, Ar, dry air). The control of the gas pressure in the deposition chamber allows to vary the morphology of the deposited films (studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM)) ranging from a compact ultrasmooth structure to a porous nano and mesostructure characterized by a high fraction of voids and by a large specific area. The presence, the structure and the degree of crystallinity of tungsten oxide have been investigated by Raman spectroscopy. By varying the pressure of the background inert gas (He, Ar) in the 1–1000 Pa range we obtain metallic films with different degrees of spontaneous oxidation when exposed to the atmosphere. Deposition in dry air permits to grow nanostructured tungsten oxide films characterized by different degrees of crystallinity, ranging from amorphous to nanocrystalline.