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

Zinc oxide was electrodeposited from oxygenated aqueous solutions of zinc c hloride at 80 degrees C on tin oxide covered glass substrates. A new activa tion treatment for the substrate is established. This consists in the initi al formation, in the deposition solution, of a thin metallic zinc layer (5- 50 nm) converted to ZnO by in situ reoxidation. Variable densities of nucle ation centers (with values approaching 10(10) cm(-2)) are formed by this tr eatment. This allows control of the formation of a zinc oxide layer ranging from open deposits of isolated crystallites to compact and homogeneous lay ers. Compact layers have high specular transmission below the band gap valu e (similar to 3.5 eV), whereas open films exhibit extensive light scatterin g. The shapes of the current-time curves during deposition are discussed in terms of nucleation and structural effects. A possible influence of the se miconducting properties of the films is pointed out.