AN AES STUDY OF THE OXIDATION OF POLYCRYSTALLINE ZIRCONIUM AT ROOM-TEMPERATURE AND LOW OXYGEN PRESSURES

Auger electron spectroscopy has been used to characterize the oxidation of polycrystalline zirconium in an oxygen atmosphere at low pressures (10** minus **8 less than equivalent to P(O//2) less than equivalent to 10** minus **5 Torr) and room temperature after cleaning the surface by Ar** plus -ion bombardment. Quantitative analysis of the oxidation process was performed by using the intensity of the Zr(M//4//5N//2//3N//4//5) line which is characteristic of the metallic zirconium. It is concluded from this work that oxidation proceeds as follows: (i) dissociative chemisorption for oxygen exposures lower than 2 L; (ii) formation of nuclei of oxide which grow until coalescence for exposures between 2 and 60 L; (iii) thickening of the oxide film grown in the previous stage. A limiting thickness of 1. 5-2 nm is estimated.