Multifunctional thin film sensors based on amorphous diamond-like carbon for use in tribological applications

Amorphous diamond-like carbon films are well known for their excellent tribological properties. In this paper, we will discuss the sensoric properties of multifunctional a-C:H films with respect to force/load/pressure and temperature measurement. It turned out that nanostructured amorphous carbon films showed an impressive piezoresistive effect. Unlike well known strain gages and piezoresistive sensors, which detect a deformation of the base substrate, this novel sensor can be used in a complete stiff arrangement without any elastic joint. For film preparation, rf-plasma CVD processes were used. Besides gas pressure, a variation of the substrate power and bias potential was performed. It turned out that the tribological parameters varied slightly (hardness: 20-30 GPa, friction coefficient: 0.10 to 0.15), whereas the electrical parameters showed remarkable differences with respect to the electrical resistivity and piezoresistivity. This paper will also present different applications of amorphous carbon thin film sensors.