Figure 6 shows the SEM image of coating No. 6 in which a columnar layer structure is observed for all coatings. The thin titanium adhesion layer, with an average layer thickness of 0.2 μm, has a defect-free interface to the substrate material in all coating experiments. The layer structures of the titanium dioxide coatings are consistently homogeneous, free of defects, and display feature defect-free bonding to the adhesive layer while there is no significant change in the layer structure between coating experiments No. 1 to No. 9.