Chemical Vapor Deposition of Al2O3 Layer on Aluminum Anodic Oxide Films Formed in Oxalic Acid Solution

Chemical vapor deposition of Al2O3 thin films on the microporous structure of anodic aluminum oxide films formed in oxalic acid solutions was examined for the purpose of surface treatment and control of the pore size of the films. Thermal decomposition of aluminum triisopropoxide (ATI) in a infrared irradiation chamber resulted in a homogeneous thin film of Al2O3. The CVD Al2O3 was deposited preferentially at the edge of the porous structure of the aluminum anodic films at an early stage of the CVD treatment. Al2O3 growth proceeded uniformly, and pore sealing was completed. CVD treatment of the anodic aluminum oxide did not cause cracks below 300°C and resulted in a uniform sealing layer at the surface. Changes in the surface morphology of the anodic alumina in the course of the CVD treatment were examined with a scanning electron microscope and the manner of the deposition of the Al2O3 film on the porous structure was discussed.