AVS 47th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThA

Paper TF-ThA7
Preparation and Properties of Transparent Conductive Aluminum-doped Zinc Oxide Thin Films by Sol-Gel Process

Thursday, October 5, 2000, 4:00 pm, Room 203

Session: Transparent Optical Coatings
Presenter: M. Alam, Dublin City University, Ireland
Authors: M. Alam, Dublin City University, Ireland
D. Cameron, Dublin City University, Ireland
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Recently, numerous electrically conductive oxides have been discovered and extensively investigated. Of these, indium tin oxide (ITO) and ZnO are well known for their transparency when made into thin films and are expected to find wide use as transparent electrodes for many devices, such as Electrochromic (ECDs), Liquid crystal displays (ELs) and solar cells. Zinc oxide is one of the most promising transparent conducting oxides currently under investigation. Zinc oxide holds considerable promise as an optically transparent conducting material due to its wide band gap (~3.3 eV), its amenability to defect or impurity doping and other desirable properties such as low cost and non-toxicity. Thin films of transparent conducting zinc oxide have been prepared by a variety of techniques, such as sputtering, chemical vapor deposition, reactive evaporation, spray pyrolysis and more recently by sol-gel process. Amongst the different techniques available, the sol-gel method seems to be the most attractive one due to coating on the desired shape and area, easy control of the doping level, solution concentration and homogeneity without using expensive and complicated equipment when compared to other methods. Highly conductive and transparent aluminum-doped zinc oxide thin films have been prepared from the solution of zinc acetate and aluminum chloride in ethanol by sol-gel process. The effect of changing the aluminum-to-zinc ratio from 0 to 6 at. % and annealing temperature from 0 to 600°C in vacuum has been thoroughly investigated. As-deposited films have high resistivity and high optical transmission. Annealing of the as-deposited films in vacuum leads to a substantial reduction in resistivity without affecting the optical transmission. The films have a minimum value of resistivity of about 1.5x10@super-3@ ohm-cm for 0.8 at. % aluminum-doped zinc oxide and a visible transmission of about 90%.