SAM INVESTIGATIONS OF TEMPERATURE-PROGRAMMED SURFACE SEGREGATION OF IMPURITIES IN ALPHA-IRON

The time development of the surface concentration of impurities such a s sulphur and nitrogen in high-purity polycrystalline alpha-iron sampl es has been investigated by means of Auger Electron Spectroscopy (AES) and Scanning Auger Microscopy (SAM) during linearly increasing the te mperature from about 100 to 850 degrees C. The subsequent segregation of N and S revealed strong differences in the segregation kinetics of these elements - especially with respect to the contribution of the do minating transport mechanism (grain boundary diffusion and bulk diffus ion). Calculating the effective diffusion coefficient of S from two su bsequent segregation runs, strongly differing values were found. An in terpretation of the change in the diffusion properties of sulphur is g iven based on SIMS (Secondary Ion Mass Spectroscopy) investigations pe rformed before and after the thermal treatment.