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Using a large beam current for fast ion milling, two trenches are milled on either side of the tungsten that has
been deposited above the area of interest. The trenches here have been milled so as to just touch the tungsten
on either side, leaving a wall of material in the centre that is approximately two to three microns thick. The trenches
themselves are approximately twenty microns wide, fifteen microns long and ten to fifteen microns deep. Before
any further thinning of the area of interest is undertaken, the beam current must be lowered. A beam of the
magnitude used to quickly cut these large trenches mills too aggressively, and lacks the precision required to
fabricate TEM specimens.
After lowering the beam current, the front face is "rough polished" to reveal
the structure of the device, which allows the operator to check for positional accuracy.
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