Morphological and structural characterization of WO3 and Cr-WO3 thin films synthesized by sol-gel process

WO3 thin films were prepared by spin-coating methanol solutions of a tungsten chloromethoxide, and easily modified with Cr by the addition of Cr 2-ethylhexanoate. The films were heat-treated up to 700 oC, and characterized by X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy and Electron Energy Loss spectroscopy. The film morphology was rough and porous, not depending on Cr presence, while their structure was constituted by packed spheroidal or elongated dense structures, giving rise to the peculiar film surface morphology. Cr was distributed in the film structure without phase separations, up to as high as 5% Cr atomic concentration.