Fabrication and characterization of electrochromic nanocrystalline WO3/Si (111) thin films for infrared emittance modulation applications

Tungsten oxide thin films with different stoichiometry have been deposited on Si (111) wafers by pulsed laser deposition (PLD) technique under different conditions. The structural properties and infrared emissivity of WO3 thin films were analysed using a scanning accessory of a transmission electron microscope (STEM), x-ray diffraction (XRD), Raman spectra (RS) and Fourier transform infrared (FT-IR) spectra. Thin films deposited at 200 degreesC on Si showed an amorphous structure, while those annealed in air at 300 and 400 degreesC showed nanocrystalline and porous triclinic structures. These porous and nanocrystalline structures could be used to improve electrochromic colour efficiency and responsing, recovery properties. However, samples deposited at 200 degreesC at d annealed at 240 degreesC for 0.5 h in oxygen showed a triclinic structure with average 10 nm crystallites. Nanocrystalline WO3 thin films on Si (111) synthesized by this technique might find applications in infrared emittance modulation systems.