Adhesion Layer
Thin coatings placed between a substrate and a functional film improve the bonding and stability of the entire stack. Sputtered metallic interlayers act as a bridge that accommodates the chemical and physical differences between two dissimilar materials. These layers are deposited in a vacuum chamber using high energy plasma to eject atoms from a source target.
Stress Management
Internal tension in thick ceramic coatings can lead to delamination if not properly controlled. By introducing sputtered metallic interlayers, the system can absorb some of the strain through ductile deformation. Titanium or chromium are frequently chosen for this purpose because they form strong bonds with both oxides and metals.
Interface Quality
Cleanliness at the molecular level is achieved by sputter etching the substrate before the metal is applied. This preparation ensures that sputtered metallic interlayers are free from contaminants that would weaken the bond. The thickness of the layer is monitored in real time using a quartz crystal microbalance to maintain precision within a few nanometres.
Performance Verification
Pull tests and scratch tests provide quantitative data on the strength of the interface. If the sputtered metallic interlayers are effective, the failure occurs within the coating or the substrate when the interface is secure. Thermal cycling is also used to ensure that the stack can withstand the expansion and contraction found in real world applications.
Engineers qualify the process by checking for any signs of blistering or peeling after exposure to extreme heat and humidity.
