Grain Orientation Contrast
FIB combines the capability of specimen preparation and imaging all in one. In-situ, "stress-free" sectioning using a finely focused beam of gallium ions has proven to be a powerful tool in the analysis of materials science specimens. Channeling contrast induced by FIB is more than four times as intense as that produced by backscattered electrons in the SEM, and results in spectacular grain contrast, as can easily be seen in the FIB image of aluminum grains on this page.
Correlation Between Grey Level Variation of Individual Al Grains and Sample Tilt
FIB secondary electron mode orientation contrast of a fully annealed, nominally pure poly-crystalline aluminum specimen changes the intensity (grey level) of each grain as a function of deviation from normal incidence as the specimen is tilted with respect to the gallium beam. The same region is imaged (inset) at angles of 0, 15, and 30 degrees tilt (foreshortening due to tilt angle is evident). The change in intensity (in arbitrary "grey level" units) is plotted as a function of tilt angle in one degree increments. Dark grains (low intensity) represent significant channeling of the primary ions. The angular width of channeling "troughs" and the angular distance between troughs can be used to calculate the relative orientation of different grains.