Oxidation of Metallic Aluminum Studied by Electrospray Droplet Impact/X‐Ray Photoelectron Spectroscopy (EDI/XPS)

ABSTRACT The oxidation processes of metallic aluminum (Al) are complicated due to the formation of intermediate oxide products. In this work, detailed X‐ray photoelectron spectroscopy analysis of the metallic Al and Al 2 O 3 irradiated by water droplet beams produced by electrospray of aqueous solutions was performed. When metallic Al was left in vacuum with a vapor pressure of P (H 2 O) = 7.4 × 10 −6 Pa, Al 2 O 3 was formed as a major product. On the other hand, by the water droplet beam irradiation on metallic Al, the formation of pseudoboehmite AlO(OH) along with the Al 2 O 3 occurred. Although it was confirmed that Al 2 O 3 could be formed on the Al surface irradiated by the water droplet beams, the simultaneous formation of AlO(OH) and Al 2 O 3 makes it difficult to apply water droplet beam etching to the interface analysis of Al 2 O 3 /Al. It is concluded that the oxidation mechanism of metallic Al irradiated by the water droplet beams differs from that formed when left in vacuum.