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 vapour and humid laboratory air. The oxide growth during the low exposure range (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 that the oxidation process can be divided into three reaction regimes: (1) an initial chemisorption stage up to exposures of ca 0.7 L; (2) nucleation and growth of oxide islands until coalescence at ca 5 L; and (3) bulk oxide thickening best described by inverse logarithmic kinetics. (C) 1997 Elsevier Science B.V.