Effect of SnO2 Coating on the Structural, Optical, and Electrical Properties of TiO2 Nanowires Fabricated by a Two-Step Deposition Method

Abstract

The photosensing properties of SnO₂-coated TiO₂ NWs have been fabricated by a two-step sequential deposition method; a thermal oxidation method followed by a hydrolysis method. Pure TiO₂ NWs show vertically aligned and uniformly distributed NW arrays on Ti foil. It was observed that the SnO₂ coating accumulated on the TiO₂ NW surfaces with increasing Sn concentration. It filled the spaces between the NWs and finally covered the entire surface of the 100 mM SnO₂ concentrated sample. The presence of increased Sn concentration on the surface was qualitatively determined by EDS and XPS measurements. The PL intensity decreases as the SnO₂ coating increases, indicating recombination retardation. Coating thickness also decreases the band gap since electron excitation requires less energy. Since electrons are easily excited by the conduction band of TiO₂, SnO₂ coatings can form an energy level within the band gap. The highest photosensitivity was 142.05% with 100-mM SnO₂-coated TiO₂ NW arrays. An alternative approach to photosensitive UV devices can be made with 100-mM SnO₂-coated TiO₂ NW arrays due to their excellent light absorption properties and efficient charge carrier generation.