Field ion microscope studies of solute atoms in dilute Pt alloys—I. Contrast due to Au, Ni and W atoms

Abstract

Platinum based alloys containing dilute concentrations of either gold, nickel or tungsten atoms were examined in the field ion microscope during pulsed field evaporation. The contrast patterns produced by the solute atoms were established by comparing the images of the alloy specimens, which contained known concentrations of solute atoms, and the images of pure platinum control specimens. The gold and nickel atoms appeared as α-dark spots, i.e. single dark atomic sites lying within net planes which were visible during all stages of the pulsed field evaporation. In many cases platinum atoms near solute atoms were preferentially field evaporated producing β-dark spots, i.e. single dark atomic sites which appeared suddenly within a well resolved net plane during observation and remained there until all the atoms of that plane evaporated. The tungsten atom contrast was more complex and generally consisted of a cluster of contrast effects which often contained multiple a-dark spots, β-dark spots and also bright spots.