Is a holey film, in which a pattern of various hole sizes, shapes and arrangements is repeated. In addition to circular holes, the pattern includes oval-shaped ones which appear round at high tilt angles (~70°). The diameters of the round holes are about 1, 1.4, and 2 µm, and the bar widths range from 0.5 to 4 µm. The oval holes in the foil have a dimension of 8 x 2 µm and 4 x 1 µm.