Electrical and optical properties of Al doped Zno film prepared by spray pyrolysis technique

Transparent conducting thin films of zinc oxides and aluminum doped zinc oxide (AZO) were prepared by the spray pyrolysis technique using an aqueous solution of dehydrate zinc acetate (CH3COOH. 2H2O, pure- Merck A. R. grade) and hex hydrate aluminum chloride (AlCl3 .6H2O) on the micro glass slides. The prepared thin films are found to be highly adherent to the substrate and possess uniform conduction. The optical and electrical properties of the film were investigated in terms of different Al concentration in the starting solution and different substrate temperature. Four probe method in Van der pauw configuration was used for electrical resistivity measurements. The resistivity of Al doped film is observed to vary with doping concentration. The lowest resistivity is observed in the film doping with 2 at % [Al/Zn]. The Hall coefficient measurements show that both ZnO and AZO show the n-type conduction. The carrier concentration was observed to be highest at 2 at% of Al doping. The optical measurements of all the samples with aluminum concentrations was found to be >85 % showing the film to be highly transparent in nature. With increase in Al concentration, the optical band gap was observed increase from 3.27 eV to 3.41 eV.