UN CO RR EC TE D PR OO F 2 Corrosion of epitaxial Fe ( 0 0 1 ) films studied 3 with CEMS and AFM

10 Epitaxial Fe(0 0 1) films of a high crystalline and surface quality, as checked in situ with AES, low energy electron 11 diffraction and STM, were grown on MgO(0 0 1). Such films show an exceptional corrosion resistance remaining me12 tallic for years at the ambient atmosphere, except of 5–10 nm, as found using the conversion electron M€ ossbauer 13 spectroscopy (CEMS). For more systematic corrosion studies, 50 nm iron films were prepared of the Fe isotope. As14 prepared Fe films, exposed to the atmosphere did not show clear morphological and compositional changes, which 15 could be associated with the oxide formation, as checked with contact AFM in air and with CEMS. After exposure of 16 the film to HNO3 or HCl vapors corrosion was observed with AFM. It resulted in two different types of surface 17 modifications. The first one was seen as a homogenous granular layer with the height amplitude of about 15 nm. 18 Corrosion-induced changes of the second type have a localized character resulting in micrometer sized porous pro19 trusions. The corrosion products were identified as c-FeOOH. Controlled oxidation of surface iron layer to epitaxial 20 Fe3O4 passivated the film. 2002 Published by Elsevier Science B.V.