SULFUR SEGREGATION ON POLYCRYSTALLINE NICKEL - ARTIFACTS FROM CRYSTALLOGRAPHIC EFFECTS IN THE AUGER SIGNAL

Sulphur segregation levels on various grains of a polycrystalline nick el sample have been measured. If the high-energy nickel Auger signal i s used as a reference, variations of up to 30% in the S/Ni ratio are s een. This large change in sulphur level results from crystallographic effects, as evidenced by the different variation of the high- and low- energy nickel Auger signals as the specimen tilt angle is varied. Of t he two processes responsible for such effects, primary beam channellin g and Auger electron diffraction, the latter is found to be important. Use of the background as a reference reduced the variation of the sul phur signal to within the error bars of the measurement of similar to 10%.