부산대학교 도서관

The growth of thin 0-200/sup 0/C has been studied as a function of time and oxygen partial pressure using proton- induced X-ray emission (PIXE) and Auger electron spectroscopy (AES). Oxidation was found to be initially retarded by sulfur which had segregated onto the iron surfaces during preoxidation annealing, but only if the iron surface contained the maximum or near-maximum sulfur coverage (ca. one-half monolayer). During and immediately following the oxygen- sulfur interaction, oxide buildup appeared to be limited by a surface reaction (adsorption, ionization, or dissociation). For most of the oxidation period, pressure-dependent logarithmic oxide growth was observed at 200/sup 0/C, and pressure-independent parabolic oxide growth at 300/sup 0/C. Interpretation of the data indicated that oxide growth at 200/sup 0/C may be limited by quantum mechanical tunneling of electronic species through the previously formed oxide film, and oxide growth at 300/sup 0/C may be limited by ionic diffusion through the previously formed oxided film. Comparison of AES and PIXE data indicated that oxide films formed at 200/sup 0/C were uniform in thickness over the surface of the metal, whereas films formed at 300/sup 0/C had relatively thin areas where sulfur had remained.