This paper describes characteristics of the tungsten trioxide (WO3) films fabricated on a glass substrate by a sol-gel spin-coating method. Ammonium meta-tungstate (AMT) and poly-vinyl alcohol (PVA) were used as the solute and stabilizer materials, respectively. The advantage of AMT is the high solubility in water, giving the capability for highly concentrated and alkali-metal-free aqueous solution. The fabricated films were characterized by x-ray diffraction, atomic force microscopy, optical transmittance spectroscopy, and Hall-effect measurement. By sintering the spin-coated solution in air, α-axis oriented orthorhombic-phase polycrystalline WO3 flat films were obtained with a bandgap energy of ∼2.8 eV and a relatively high electron mobility of ∼30 cm2/Vs. These results indicate that the sol-gel spin-coating method can be promising for the fabrication of semiconducting WO3 films to apply electronic devices.
