3.1.7. Surface Roughness

Stylus profilometry was performed on coatings to assess surface roughness and morphology. Figure 8 shows measured Ra values for uncoated polished CPTi, HA and SiHA coated discs. Uncoated CPTi discs had an Ra value of ca. 16 nm and their roughness increased to ca. 25 and 70 nm after heat treatment at 600 and 700 ◦C, respectively. As deposited HA and all SiHA coatings exhibited similar roughness, ca. 20 nm. After heat treatments at 600 ◦C, HA films had the highest roughness value at ca. 41 nm, which decreased gradually with increasing silicon content. This effect was also observed for all films heat treated at 700 ◦C, but at significantly higher roughness values than the samples treated at 600 ◦C, with HA films having a roughness of ca. 78 nm, and the SiHA3 samples being measured at ca. 32 nm.

**Figure 8.** Ra roughness values for CPTi, HA and SiHA thin films as received and heat treated at 600 and 700 ◦C in flowing argon for 2 h.
