Moisture barrier properties of low-temperature atomic layer deposited Al2O3 using various oxidants

In this study, the growth characteristics and film properties of the atomic layer deposition (ALD) of Al2O3 are systemically identified using various oxidants (i.e., H2O, H2O2, CH3COOH, and O3). Among these reactants, ALD Al2O3 grown by using H2O2 exhibits excellent density and refractive index, which may be attributed to the large number of hydroxyl groups on the surface after reactant exposure, forming a dense film. When CH3COOH is used for the ALD Al2O3 oxidant, poor quality films with relatively small density and refractive index and high carbon impurities were deposited possibly due to the formation of carbon species, such as carbonates or formates. In the case of ALD Al2O3 that uses O3, the film property is barely changed with the growth temperature increase because the reaction between trimethylaluminum and O3 is incomplete in low-temperature region (<150 °C), and impurities that are difficult to eliminate remain. Among these Al2O3 films prepared by using different oxidants, H2O2-grown Al2O3 at 120 °C exhibits the lowest water vapor transmission rates, ca. 2.7 × 10−4 g/m2⋅day, owing to the high density of the film with negligible amount of impurities. Therefore, ALD Al2O3 using H2O2 is expected to be a promising encapsulation layer for future flexible OLED devices with excellent characteristics.