8 Speckling and Testing with DIC at Microscales 69 Fig. 8.2 As-polished surface features on an aluminum sample, 1.2 mm by 1.0 mm field of view Fig. 8.3 As-manufactured surface features on a second level copper pad paints could be used with an airbrush and produced acceptable contrast for tracking (Fig. 8.4). Even with sufficient contrast, the feature size with airbrushed paints was too large for the fields of view being attempted. Another technique used for creating a pattern is the use of micro stamp SEM pads. These stamp pads are intended to create a topography for performing DIC in an SEM but can be used on reflective substrates to create an optical pattern. These stamps are designed to have a 1 μm feature size. Unfortunately, the consistently of the pattern was poor (Fig. 8.5). Strips of useful pattern are separated by less distinct regions. Even at the smallest field of view, the distinct areas were not large enough to cover the image. Due to the variability in definition, this technique is also not suitable for covering a particular area of interest on a specimen.
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