Effect of 3-D heat flow near edges in photothermal measurements.

Photothermal imaging scans often show large signal enhancement at sample edges. This effect can be attributed to 3-D heat flow within the sample. Geometric constraints which limit 3-D heat flow generally increase the sample surface temperature and the photothermal signal. The dependence of edge enhancement on sample thermal and physical dimensions is investigated for several systems containing one or more edges. Results suggest that geometrically restricted heat flow might explain the enhanced photothermal signal obtained for powders and other textured surfaces.