Transparent semiconducting ZnO:Al thin films prepared by spray pyrolysis

Aluminum doped zinc oxide (ZnO:Al) films which can be used as transparent electrodes or heating layers have been deposited by the low cost spray pyrolysis technique. Undoped and Al-doped ZnO films deposited using various preparation conditions and on different substrates (soda lime glass, quartz glass and crystalline quartz, respectively) have been studied. The effect of substrate type, temperature, deposition time and doping concentration on ZnO:Al thin layers have been investigated by analysing the optical and structural properties of the films. A substrate temperature of 770 K allows the preparation of nanosized ZnO:Al crystals with preferred [002] orientation. Films with optical transmission T > 85% and a adjustable resistivity rho between 2 and 100 Omega cm have been obtained. The resistivity value of the films can be adjusted by tuning suitable processing parameters. The feasibility of the spray pyrolysis technique for the preparation of thin semiconducting ZnO:Al films on conventional soda lime glass substrates is demonstrated. (C) 1999 Elsevier Science Ltd. All rights reserved.