Loss of Grain Boundary Segregant During Ion Milling.

摘要

Bismuth segregates to grain boundaries in copper at intermediate temperatures (400--800C). Currently, x-ray microanalysis is being used to measure the degree of equilibrium segregation as a function of boundary character. As part of that study, transmission electron microscopy specimens were prepared by several techniques in order to select that method which produced optimum specimens. Electropolishing produced specimens of marginal quality because of preferential grain boundary attack. On the other hand, ion-milling produced good, thin specimens with little or no boundary attack. However, x-ray microanalysis on specimens ion-milled at room temperature indicated no bismuth segregation, whereas analysis on electropolished specimens indicated bismuth segregation. A loss of bismuth from the ion-milled specimens was proposed to result from the high vapor pressure of bismuth at slightly elevated temperatures. The use of a liquid nitrogen cold stage during ion-milling minimizes the loss of bismuth. It is likely that beam heating during ion-milling is a contributing factor in this process and must be controlled. 9 refs., 3 figs.