Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 30: Layer Properties: Electrical, Optical and Mechanical Properties

DS 30.6: Vortrag

Donnerstag, 28. Februar 2008, 10:45–11:00, H 2032

Determination of yield stress and elastic modulus under complete consideration of substrate influence demonstrated on a-C:H films — •Matthias Herrmann, Maksim Karniychuk, Siegfried Peter, and Frank Richter — Institute of Physics, Solid State Physics, Chemnitz University of Technology, Germany

Much attention has been given to the mechanical response of diamond-like carbon (DLC) coatings such as amorphous hydrogenated carbon (a-C:H) because of their widespread applications as protective films for magnetic storage disks, optical parts, MEMS applications, and so forth. However, to successfully integrate DLC films into three-dimensional structures, a deeper understanding of the mechanical response of the films becomes necessary which can no longer be carried out by standard hardness testing. This is mainly addressed to more complex stress states within the material. To overcome this, the determination of parameters for elastic deformation (i.e. elastic modulus and Poisson's ratio) and critical stress states for the onset of inelastic deformation is expected to be more feasible for mechanical performance qualification. In the present study, a-C:H coatings deposited by a capacitively coupled r.f. PECVD process have been investigated in order to determine the film modulus, yield stress and yield strain. Therefore instrumented indentation experiments with spherical tips for elastic deformation and standard tests with sharp tips have been performed. The latter one enables to derive the yield stress from hardness tests by applying Pharr's concept of the effective indenter. The mechanical film properties are discussed in terms of the ion energy per deposited C-atom.