Reliability of sputter deposited aluminum-doped zinc oxide under harsh environmental conditions

We report the reliability of aluminum-doped zinc oxide (AZO) thin films exposed to harsh environmental conditions of damp heat. Identical sets of the AZO films grown on float glass substrates were subjected to four different controlled environments of temperature and relative humidity. The selected high and low levels of the temperature were 100 degrees C and 20 degrees C respectively and the selected high and low relative humidity levels were 100% and 20% respectively. The total exposure time for this controlled environment was 120 h. Electrical resistance was measured every 24 h for each sample. Material composition, crystallinity, optical transmittance and surface morphology of the films were investigated after 120 h exposure time. A mixed, full-factorial design of experiment was used in this study, with the response being the electrical resistance. The factors were exposure time, temperature and humidity. The ANOVA results showed that all the considered factors were significant. Although the electrical resistance of the film exposed to high temperature and high relative humidity increased by 20%, the microstructure in the bulk of the film, crystallinity and optical properties of the films exposed to all combinations of temperature and humidity were unchanged. (C) 2012 Elsevier Ltd. All rights reserved.