THE OXIDATION-KINETICS OF MG AND AL SURFACES STUDIED BY AES AND XPS

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) have been used to study the oxidation kinetics of pure aluminum and magnesium surfaces across a wide range of exposure to water vapou r and humid laboratory air. The oxide growth during the low exposure r ange (up to 10 L, 1 L = 1.33 x 10(-14) Pa.s) was examined by AES, and during the high exposure range (from 50 L to 1 x 10(6) L in ultra-high vacuum and to 1 x 10(14) L in laboratory air) by XPS. It was found th at the oxidation process can be divided into three reaction regimes: ( 1) an initial chemisorption stage up to exposures of ca 0.7 L; (2) nuc leation and growth of oxide islands until coalescence at ca 5 L; and ( 3) bulk oxide thickening best described by inverse logarithmic kinetic s. (C) 1997 Elsevier Science B.V.