Nucleation effects on structural and optical properties of electrodeposited zinc oxide on tin oxide

Abstract

Zinc oxide was electrodeposited from oxygenated aqueous solutions of zinc chloride at 80 ∘C on tin oxide covered glass substrates. A new activation treatment for the substrate is established. This consists in the initial formation, in the deposition solution, of a thin metallic zinc layer (5–50 nm) converted to ZnO by in situ reoxidation. Variable densities of nucleation centers (with values approaching 1010 cm−2) are formed by this treatment. This allows control of the formation of a zinc oxide layer ranging from open deposits of isolated crystallites to compact and homogeneous layers. Compact layers have high specular transmission below the band gap value (∼3.5 eV), whereas open films exhibit extensive light scattering. The shapes of the current–time curves during deposition are discussed in terms of nucleation and structural effects. A possible influence of the semiconducting properties of the films is pointed out.