Transparent and conductive W-doped SnO2 thin films fabricated by an aqueous solution process

High-quality transparent and conductive tungsten-doped tin oxide (SnO 2 :W) thin films with different thickness (from 60 to 600   ±   10   nm) were fabricated on quartz glass substrates by a solution-based method. A stable solution was prepared from tin chloride and ammonium tungstate together with polyvinyl alcohol as a film-forming promoter. It was found that all films showed homogeneous composition, smooth surface with no cracks and high transparency with the optical band gap ranging from 3.93 to 4.31   eV. The effect of tungsten concentration, spin rate and annealing temperature on the morphological, electrical and optical properties of the films has been investigated. W doping has a large influence on the microstructure and the conductivity of the SnO 2 thin films . The lowest resistivity of 2.8   ×   10 −   3 Ω   ·   cm was obtained for a SnO 2 : 3 at% W film, which was prepared at 3000   rpm and annealed at 800   °C in air. An eight-layer film with a sheet resistance of 60 Ω/□ and a thickness of 606   nm could be fabricated by multiple coating operation, which still exhibited an optical transmittance of over 80% in the visible region from 400 to 700   nm.