Multi-Layer Films
Multi-layer films are often deposited to combine the favorable properties of different materials such as sufficient toughness and high hardness.
It is of interest to control the quality of the critical component in such layer-compounds.
Figure 1 shows measurements of multi-layer films consisting of diamond-like carbon (DLC) and aluminum (Al) deposited on steel.
Film composition:
Film 1:
Film 2:
Figure 1: Laser-acoustic results for multi-layer films consisting of different numbers of diamond-like carbon and aluminum single layers
The software can directly provide the modulus of one of both film components on the condition that the parameters of the other film are known. Young’s modulus of the aluminum layers was assumed to vary only little compared to the tabulated value (E = 70 GPa ). This was not expected for the diamond-like carbon layers. Testing their quality is highly desirable because of their essential effect on the wear resistance. The obtained values of EDLC = 394 and 380 GPa indicate that diamond-like carbon of similar quality was deposited in both multi-layer films.
Multi-layer films show different mechanical properties in-plane and perpendicular to the surface, described by transversal anisotropy.
The software is able to provide the elastic constants for this anisotropy.
Tension modulus for Film 1:
in-plane: C11 = C22 = 348 GPa
perpendicular: C33 = 266 GPa
Tension modulus for Film 2:
in-plane: C11 = C22 = 429 GPa
perpendicular: C33 = 420 GPa
Comparing the elastic parameters in-plane and perpendicular to the film for both films points out that a higher number of aluminum layers increases the anisotropy of the film and reduces their effective stiffness.