| Ti interlayer thickness (nm) | a-C:H film thickness (nm) | Adhesion strength (µN) |
| 5 | 350 | 435 ± 71 |
| 35 | 350 | 1690 ± 50 |
| 70 | 350 | 1080 ± 44 |
| 35 | 700 | 1132 ± 54 |
| 70 | 700 | 1037 ± 90 |