Moisture-induced surface corrosion in AZO thin films formed by atomic layer deposition

Aluminum-doped zinc oxide (AZO) thin film is a viable alternative to tin-doped indium oxide, the dominant transparent conducting oxide used in solar cells. The durability of the AZO thin films grown by atomic layer deposition technique, which is known to form layers with atomic layer precision, is studied. The AZO films were subjected to the harsh environmental conditions of varying temperatures and humidity, and their changes in surface morphology and conductivity are investigated. Four different combinations of temperature (100 °C and 20 °C) and relative humidity (100% and 20%) were used. It was found that the films exposed to the high-moisture and temperature conditions resulted in surface corrosion and lowered conductivity. However, SEM cross-sectional images showed that the bulk of the film was unaffected. The corroded surface had contaminants deposited from the measurement chamber as observed from XPS elemental analysis. Detailed phase analysis showed the presence of zinc hydroxide and zinc carbonate inside the corroded regions.