Anywhere large numbers of people gather, touch-based contamination contributes to the spread of bacterial infections. Coatings with antibacterial effect could have an important public health benefit. This includes door handles, bathroom taps and other high-touch elements in public and private buildings. Already for decades these elements have commonly had a PVD decorative finish, which provides them with an attractive look and increased wear and corrosion resistance. The next generation decorative coating should also include antibacterial properties.

Hard coatings deposited by physical vapor deposition are usually subjected to high residual stress. To relieve the residual stress, it is commonly introducing a metal interlayer between coating and substrate or by further coating architecture design. However, the underlying stress relief mechanism of coatings with architecture has not been fully understood. The purpose of this study was to investigate the extent of stress relief achieved by employing different types of interlayers or coating architecture, and explain the stress relief mechanism in each coating architecture using a simple energy-balance model. Themodel was based on the concept that the relief of stored energies from both coating (ΔG_f) and Si substrate (ΔG_Si) was converted to the plastic work by the metal interlayer. TiZrN/TiN/Ti tri-layer coatings and TiZrN bi-layer coatings with Ti, TiZr and TiZr/Ti interlayers on Si substrate were chosen as the model systems, which were deposited using unbalanced magnetron sputtering. Laser curvature method and the average X-ray strain method combined with nanoindentation were used to measure the residual stress of the entire specimen and individual layers, respectively. For the TiZrN specimens with different interlayers, the results showed that increasing the metal interlayer thickness may not be an effective way on increasing stress relief efficiency in the coating. Since plastic deformation of the interlayer could only occur in part of the interlayer near the TiZrN/interlayer interface, increasing the interlayer thickness did not substantially increase the effective deformation thickness. Furthermore, plastic deformation became difficult for the metal interlayer with higher strength coefficient (k). Therefore, ΔG_f may decrease by using high-k interlayer with the same thickness. However, the high-k interlayer could act as a channel to transfer the stress to the Si substrate, if proper interlayer thickness was used. For the specimens with coating architecture, the results revealed that the extent of stress relief in TiZrN coating with TiN/Ti architected interlayer was larger than that with only a single Ti interlayer. The TiN transitional layer served as an energy channel that effectively transferred the stored energy in TiZrN to the Ti interlayer and alleviated the large stress difference at the original TiZrN/Ti interface, thereby increasing the plastic deformation capacity of the underlying interlayer; therefore, a larger fraction of residual stress in TiZrN was relieved.